Hey @Logan_Brokenspark! Aetherlight works on computers and tablets. They don't have them for phones, that I know of. The Aetherlight is both on the Apple store and Google play store if he is on a tablet. Otherwise, if he is on a computer, he can just type into Google search "Aetherlight: Chronicles of the Resistance" and their site will pop up. Then through their site, they have the option to download it either on a windows computer or on an Mac.
He can also go to their site if he has a tablet and it gives options to download from their as well.
I can post pictures if you need in order to show your friend where to go. If he is trying to get Aetherlight on his phone, that might be why he isn't able to find it.
If you can find out what he has, we can help a little bit more, and then if needed, we can walk you guys through the process!