Step 1 : Download Xexmenu 1.2 and extract it to your desktop.
Step 2 : Go into the folder you just extracted and keep opening the folders untill you see C0DE99990F586558 file.
Step 3 : Open Horizon and plug your xbox configured usb into your computer
Step 4 : Once you have your configured usb into your computer and opened horizon go to device explorer.
Step 5 : Open your usb in device explorer right click on demos and select inject file then navigate to the file called C0DE99990F586558 that your extracted earlier wait 5-10 mins for the file to be put on your usb.
Step 6 : Unplug your usb from your computer plug it into your jtag / rgh on the console go to system settings then storage and select your usb. Go into your demos folder on your usb you will see xex menu 1.2 click on that and move it to your hard drive.
To use it go to dashboard go over to games then my games and it will be there.