Just as with the standalone GZDoom, you can pass commands through using the command line. If you want to play custom wads, you can add them to a sub-directory of `/gzdoom/` and then you can directly access then from the terminal:
If you want to access wads in different locations, you might have to adjust the [Flatpak sandboxing permissions](http://docs.flatpak.org/en/latest/sandbox-permissions.html). You can easily do that like this:
