Q: AIRPORT EXTREME WI-FI

Just to make sure I understand your networking goals ... is the AirPort Extreme going to be the "main" base station that you will be extending with the AirPort Express?

Will the connection between them be a wired or wireless one?

Ok, thanks for the additional information. I am going to assume that the Extreme will be the main base station and you want to extend it with the Express.

A few things to get started:

• Perform a "factory default" reset on both base stations. Leave both powered-off when completed.
• Have both base stations in the same room during the set up phase. You can move the Express to the desired location after we verify that the extended network has been properly configured.
• Connect an Ethernet cable between the Ethernet/LAN port on the modem and the WAN (circle-of-dots) port on the AirPort Extreme.
• Power-up (plug the Extreme into a power outlet). Wait for at least 5 minutes for it to initialize. The base station's status LED should be flashing amber.

From your MacBook Air:

• Verify that Wi-Fi is enabled.
• Click on the Wi-Fi icon on the OS X's menu bar.
• The Extreme should now show up under "New AirPort Base Station."
• Click on the base station.
• That should start up the AirPort Utility.
• Go through the utility's automated setup to create a wireless network.
• When completed, you should have an operational Wi-Fi network with Internet access.

Verify that this worked and you can access the Internet with your MacBook Air. Please post back your results. If successful, we will go on to adding the Express for an extended network.

My problem is that when choosing to ;join an existing network"

After clicking the "ok" it should show up Abby existing access points

Available but doesn't.

Looks like you got ahead of yourself. I was hoping that you would report back before attempting to configure the Express for extending the Extreme.

For extending, the correct option for the Express is "Extend a wireless network."

Please review the Setup Guide that came with the AirPort Extreme, and steps that Tesserax has provided for you above to confirm that it must connect to a modem or modem/router using a permanent wired Ethernet cable connection.

When you do this, the setup utility will automatically suggest the correct setup for you, which is "create a wireless network".  You do not need to select the Other Options button at all. The illustration below shows an older AirPort Express, but you will see your AirPort Extreme pictured on your screen.

Click Next and follow the prompts to configure the AirPort Extreme.  Once the AirPort Extreme has been configured.....then....you can set up the AirPort Express to "extend" the wireless network that the AirPort Extreme is providing.

The point is that the Extreme must be connected to your modem by Ethernet. The Express will be a wireless connection to the Extreme for extending it.

What is the make & model of the modem that you will have the Extreme connected to?

I don't want to have it connected to a router.

If the point is that if the extreme does not work as

Extender then is useless.

All AirPort base stations can extend other AirPort base station with a wireless connection between them ... so the Extreme can be used as an Wi-Fi extender ONLY if the base station that it is extending is another AirPort base station.

If you want to extend another manufacturer's product, you will not be able to do so with the Extreme with a wireless connection between them.

I can't extend any other wifi network when the "Express"is able to.....

The Express can only wirelessly "extend" the network provided by another Apple router. If the Express is connected to the wireless of your modem/router, then it is NOT extending that network. 

Instead, the Express is joining the network, meaning that it could be used for AirPlay or allow a compatible USB printer to connect. But the Express will not provide additional wireless coverage for your modem/router wireless, if that was what you were thinking.