If you want to play games on Retro Game HAT, you need to install a game system, here we select RetroPie.

RetroPie allows you to turn your Raspberry Pi, ODroid C1/C2, or PC into a retro-gaming machine. It builds upon Raspbian OS, Emulation Station, RetroArch and many other projects to enable you to play your favorite Arcade, home-console, and classic PC games with the minimum set-up.