Disclamer: This only works for Apple TV's and IPads
This is supposing that the person installing the Apple TV already spoke to someone with admin login and created a user for the device. Plus having all the details about it on hand.
1) Start up the Apple TV or IPad
2) Start the App Store and Log in if needed (if you don't have credential ask the client to create an account and give you the details)
5) Then add a M3U Channel Lsit, click on “Add M3U channel list”. Enter the URL the admin gave you, looks something like this; https://tvapi.mixvoip.com/Api/m3u/thisisamac123/000000000000/ (please note that the last / is very very important)