In this guide we are going to walk through setting up a Ubiquiti UAP Educational Access Point/Speaker, registered as an Extension in a Grandstream UCM62XX PABX.
You will need to configure your Grandstream UCM PABX and Ubiquiti Unifi AP's with a base setup before you can follow this guide.

Login to your UCM and go to "Extension / Trunk" > "Extensions" > "+ Add" and add a new extension (you can specify the extension number if you like).

Copy and paste the "SIP/IAX Password:" or set your own and now open up the UniFi software.
In the UniFi software go to "Settings" > "Services" > "SIP" > "Configuration" and make sure that "Enable EDU SIP Client" is on and the "SIP Server" has the domain name or IP address of the UCM62XX.

Now head to "Endpoints" > "CREATE NEW ENDPOINT".

"Device" - Select the Unifi AP AC Educational you would like to configure.

"Extension/Username" - This should be the extension number you created in the PBX

"Auth User" - Blank unless you have set this in the PBX

"Password" - The SIP/IAX Password you copied or created from the new extension in the PBX.

Select "SAVE", go back to the extension you created in the PBX, the status should show a green "Idle" symbol.