Here is a process to set up the 2.4ghz on Airport Extreme for syncing to SkyBell.
1. Launch the Airport Utility.
2. Click the Airport Extreme icon and select Edit.
3. Click the Wireless tab. You'll see the name of your network in the field labeled Wireless Network Name.
4. Click the Wireless Option button.
5. Check the box labeled 5GHz network name. This will append 5GHz to the existing name or you can enter something else.
6. Click Save. Click Update. Airport Extreme will restart.
7. Now the 2.4GHz network will have the name displayed in step 3, and the 5GHz network will have the name displayed in step 5.
8. To configure the SkyBell, select the 2.4GHz name under Settings: Wi-Fi.
9. Once the SkyBell has been configured you can return to Airport Utility and uncheck the box for the 5GHz network name, if you want.