Press the button (usually three dots or your phone's back button). Select Cheats .

Access debug menus or unused sprites left behind by developers. How to Create and Use a GenPlusDroid Cheat File

Here, you can either "Add Cheat" manually or, in some versions, "Load Cheat File."

The Ultimate Guide to GenPlusDroid Cheat Files: Mastering Sega Classics on the Go