How do I change the name of my wifi network?

Use Airport Utility to change the name.

Open Finder > Applications > Utilities > AirPort Utility

Click on the AirPort Extreme icon

Click Edit in the smaller window that appears

Click the Wireless tab at the top of the next window that appears

Edit the Wireless Network Name to something that is simple, short, with no blank spaces or special characters

Change the Wireless Password to something different and Verify again

Click Update at the lower right of the window and wait a minute for the AirPort Extreme to restart

Might be a good idea to write down the new password and keep it in a safe place.