Thanks for the clarification.
But, if you have assigned the name of the wireless network that you want the AirPort Extreme to use, then you are done. Nothing else to do.
You might still see some of the "old" networks until you restart each of your Macs, as they will remember networks to which they have connected in the past.....event though they are no longer there. Give them a day or two to forget the old networks when you click the WiFi icon at the top of the Mac's screen.
If you have the time, we can give you instructions to go into the settings for each Mac and remove the names of networks that the Mac has connected to in the past. Let us know if you want to do that, but it should not really be necessary in most cases.
So, the question here would be.......if you open AirPort Utility, click on the AirPort Extreme, click Edit, and then click on the Wireless tab at the top of the screen......
Does the network name that you want to use appear next to Wireless Network Name? If yes, you are OK,
If no, then edit the settings box to enter the name that you want to use for the network.
Edit and Verify the Wireless Password if you need to make any changes to the password that you want to use.
Click Update and you are done.