Hi a.sami! Gamethrive dev here, sorry our documentation isn’t more clear about this. We’re continually working on improving it.
The best way to test push notifications is to build your app with a Development Provisioning Profile, and a Sandbox Client Push Certificate (Sometimes called a Development client certificate).
Make sure to configure your build.settings and config.lua files, as well as putting the right code into main.lua. If you did it right, you should get prompted to accept push notifications when you first run the app (Click yes). You should also see the user count go up by 1 in the Segments section of the GameThrive dashboard.
Finally, follow the directions to generate a sandbox p12 client push certificate and upload it in the GameThrive settings.
Now you should be able to send messages and receive them on your device.
Hope that helps! Let me know if anything is still unclear or not working.