What version of AirPort Extreme do you have now? If you are not sure, look on the bottom of the AirPort Extreme for the model number, which will be the letter "A" followed by 4 numbers.
You did not tell us whether you plan to extend the network by connecting the AirPort Express using a wired Ethernet connection back to the AirPort Extreme, or whether you hope to extend the network wirelessly.
Please clarify on that.
You can add a new AirPort Express to extend the wireless coverage.
You can do this by connecting the AirPort Express back to the AirPort Extreme using a wired Ethernet connection (highly recommended).......or......if the AirPort Express is located where it can receive a strong wireless signal, it can connect to the AirPort Extreme wirelessly.
If you elect the wired option, you can locate the AirPort Express right where it will be needed.
If you elect the wireless option, the Express should be located about half the distance between the AirPort Extreme and the general area that needs more wireless coverage.
Thanks for such a complete answer I appreciate. I have solid strong signal everywhere in the house so I will connect by rear door and deck wirelessly. I assume I will have to manually configure the express to amplify the existing network...
If I find that it will be stronger I will dig out the ethernet cable I had from when I set up my god daughter's network at her college.....
still have that old habit of hanging on to almost obsolete stuff.
If you need the configuration steps, and can confirm what operating system you are using on your Mac......your profile indicates the older Leopard system.....we can provide the steps.
Configuration is really easy if you have moved up to the Lion or Mountain Lion operating system. More involved with Leopard or Snow Leopard.
A few more questions may have to be asked as well.
As I said I hate throwing out old technology, lol So I keep everything until it dies...think I have almost every mac model change.
My MBPro is running 10.8.4 as are both my Imacs, then I also have a G5 Twin Tower which still runs every now and then but is suffering from the "jet plane" noise.....
steps are always welcome
You won't believe how easy it is to configure the new Express if you use 10.8.4.
Power up the new Express at its desired location, and wait for a slow, blinking amber light
Click the AirPort icon at the top of the screen on your Mac
Wait a few seconds for a listing of New AirPort Base Station to appear
Just below that, click directly on AirPort Express
AirPort Setup will open automatically, take a minute to analyze things, then announce that the Express will be configured to extend your AirPort Extreme
Enter a device name that you want to use for the AirPort Express....example, AirPort Express....and click Next
AirPort Setup will take another minute to configure everything. When you see the message of Setup Complete, click Done.