The latest pre-made image of RetroPie is v3.7 was released few days ago and you can grab your copy from this link. For those who don’t know RetroPie allows you to turn your Raspberry Pi into a retro-gaming machine. It builds upon Raspbian, EmulationStation, RetroArch and many other projects to enable you to play your favorite Arcade, home-console, and classic PC games with the minimum set-up. For power users it also provides a large variety of configuration tools to customize the system as you want. RetroPie sits on top of a full OS, you can install it on an existing Raspbian, or start with the RetroPie image and add additional software later.
Installation instructions here: https://github.com/retropie/retropie-setup/wiki/First-Installation