Download the game from a reputable source for JTAG/RGH rips. You will usually find the game in one of two formats:
Before starting, ensure your console has the necessary homebrew software installed: download forza horizon 2 xbox 360 jtag
Use a tool like Xbox 360 ISO Extract or 360MPP to extract the files into a folder. Download the game from a reputable source for JTAG/RGH rips