The Airport utility won't recognize the Airport express

If you are trying to configue the Express using wireless....

Click the AirPort icon at the top of Mac's screen

Click Join Other Network

Click Show Networks

Select the Apple Network xxxxxxx that the Express is broadcasting, no password is required

Then, open AirPort Utility

It is much easier for most users to temporarily connect an Ethernet cable from the Mac to the AirPort Express, then open AirPort Utility. Disconnect the Ethernet cable once the Express has been configured

If you're trying to bridge the existing wireless network, I found that you can't configure the Airport Express from the wired computer behind the Airport Express. I had to:

1. Unplug the AirPort Express
2. Disable the WiFi on the Mini
3. In Network Preferences, set Ethernet as the default connection using DHCP.
4. Connect the Mini to the LAN port for the AirPortExpress
5. Plug-in the AirportExpress
6. FROM A DIFFERENT COMPUTER CONNECTED TO THE WIRELESS NETWORK, follow steps 6-9 from http://support.apple.com/kb/HT1731?viewlocale=en_US&locale=en_US

This worked for me, but I don't know how to resolve the issue if you don't have a 2nd computer available. I had also tried this via Airport Utility on an 1st generation iPad, but that didn't work. Maybe somebody in the same situation could try it with an iPad that can run a newer verion of iOS.

I did this and it worked - until I got to the step in which you have to select Other. There is no Other to select. Where do I find it?