HOW TO SET UP AN AIRPORT EXPRESS AS A RANGE EXTENDER
Found this article, went through the steps, confirm it works.http://www.maccomputerlessons.com/how_to_wirelessly_join_connect_to_wireless_net work_airport_express.htm
In this section I will teach you how to wirelessly connect an Airport Express device to an existing wireless network that is associated with a wireless modem/router, as opposed to creating a new wireless network like in the previous section. In other words, the airport express device will be connected wirelessly to the wireless modem/router's wireless network. This means the airport express device is joining (connecting to) that wireless network and not its own, in the same way an ipad would join that wireless network. The advantage of this is that you can then take the airport express device, now connected wirelessly to the wireless modem/router's wireless network, into another room and then attach it to a networked hard drive, standard printer, apple tv or other internet based gadget.
I have since enabled the wireless router functionality of my NetGear R7500 wireless modem/router, by ticking and applying its ENABLE WIRELESS ACCESS POINT wireless setting, so that I now have a wireless internet connection coming from its wireless network called: Yoingco. It will be this Yoingco wireless network that I will be joining the airport express device to. I have also, purposely, reset my Airport Express device so that it's using default Factory Settings again. Although this step is not required, it can sometimes help to avoid troubleshooting later on.
Resetting was done by pressing down on the Reset Button at the back of the airport express device for about 6 Seconds until its amber light starting blinking rapidly. Although this worked, one thing worth noting here is that the Airport Utility application together with OS X (El Capitan) will try and make the airport express device recollect/remember the wireless network it was previously connected to, in order to rejoin it. This is good if you want to try and rejoin that old wireless network, but bad if you want it forgotten. In this case I want it forgotten. So before doing anything else the first step to joining a new wireless network, after a factory reset, is to remove all recollection of the old, previous, wireless network. This is done by clicking on the AIRPORT EXPRESS icon and then clicking on the FORGET button within the Airport Utility application window that appears when you first switch on your airport express device.
Fig 1.0 Click on the FORGET button to tell the airport express device to forget the previously connected wireless network
Now that the previously connected wireless network has been forgotten, the next step is to get the Airport Utility application and OS X (Mountain Lion) to recognize the airport express device again. This is done by clicking on the OTHER AIRPORT BASE STATIONS (1) drop-down menu in the top left corner of the Airport Utility application window and selecting your airport express device (base station), which should be the only one available. In this case the Airport Express 0caa7e.
Fig 1.1 Click on the OTHER AIRPORT BASE STATIONS (1) drop-down menu and select your Airport Express device (base station)
As the airport express device has been reset to factory settings and been told to forget the previously connected wireless network, the Airport Utility application is forced to set up the airport express device again; from scratch.
Fig 1.2 The airport express device is being set up again, from scratch, due to the Factory Reset earlier.
You will know when the airport express device has been, initially, set up (pre-configured) because the Airport Utility application window will display the first step of its Installation Wizard, which contains the standard "Create A Network" message and the options (buttons and menus) for creating a new wireless network or joining/extending an existing wireless network. In the example below, because you will not be creating a new wireless network, you will need to click on the OTHER OPTIONS button to proceed.
Fig 1.3 Click on the OTHER OPTIONS button to join an existing wireless network
When the Other Options appear the default setting (default option) called CREATE A NEW NETWORK will be selected. However, because you want to join an existing wireless network you need to select the setting (option) called ADD TO AN EXISTING NETWORK instead before clicking on the NEXT button.
Fig 1.4 To join an existing wireless network select the ADD TO AN EXISTING NETWORK option and then click on the NEXT button
The next step of the Installation Wizard (Airport Utility application) is to ask you which wireless network you want to join (connect to). By default you should see your currently connected, wireless modem/router, wireless network listed as the first choice, but if you have more than one wireless network available (i.e. one modem/router wireless network and a neighbour's wireless network) you can select one of them from the CONNECT TO drop-down menu. Once you have a wireless network selected click on the NEXT button to continue.
Fig 1.5 Select the wireless network you wish to join and then click on the NEXT button to proceed
With a wireless network selected you are then asked to enter a password for the airport express device (base station). Simply type your preferred password into the PASSWORD edit box, verify it by typing it into the VERIFY edit box and then click on the NEXT button. Airport Utility will then set up the rest of the airport express device for you whereby it is then connected to (joined to) the wireless network you have just selected and therefore using its internet connection wirelessly.
Note Well - The password you enter here is for the Airport Express device (Base Station) only. When joining an existing wireless network the installation wizard knows it should use the already logged in, existing, wireless network's password; that it gets from the keychain. If you are currently logged out of the existing wireless network (the wireless network you want to join) you will be asked for its password.
Fig 1.6 Give the airport express device (base station) a password - Type it into the PASSWORD and VERIFY edit boxes
Fig 1.7 Airport Utility is setting up the internet connection between your airport express device and the selected wireless network
Fig 1.8 Your airport express device is now connected to your selected wireless network, now using its internet connection wirelessly.
When you see the 'Setup Complete' message click on the DONE button (above) - You should then see following diagram with green lights, indicating a valid internet connection and joining of the selected wireless network.
Fig 1.9 The green lights indicate a valid internet connection and successful joining of your selected wireless network
So just to clarify; In the above set up process I did not have the airport express device connected to an ethernet cable. The joining of (connection to) the Yoingco wireless network was made purely by the airport express device's built-in router that was able to detect (pickup) and join the Yoingco wireless network wirelessly without cables.
