The XenoGC BIOS acts transparently leaving you with no onscreen interface. If you would like to take advantage of booting unsigned code with you will have to create a bootable DISC. This can be accomplished by following XboxModder999's excellent guide.

To boot normal games and/or legitimate backups all you do is insert a disc and turn on your GameCube. If your backup/homebrew disc fails to boot you might want to check out the Burning and DRE Guides.

Although the XenoGC does not have an GUI you are still presented with some options while booting the chip. You can adjust a few settings by holding varius buttons on controller 1 while booting. The settings will be in effect per boot and not change behavior permanently.

[L] Disable audiofix
If you modified your backup images to work with bioses that didn't support streaming audio correctly, you can disable the native fix.

[R] Disable DREfix
Turns off the native read adjustment/retries. Can be useful if you want to scan a disc for read errors. The chip will not try to prevent any errors and use the default read settings.

[X/Y] Force NTSC/PAL display mode
Will force the selected region's display mode regardless of the actual game region. This will work for some games, for others it won't.

[START] Version display
Shows some basic version info (Chip, GC and drive)

Status LEDs
The XenoGC features two status LEDs to indicate correct function. The red LED is active when the drive resets and the chip is doing its job. Once the drive has been patched successfully, the green LED will light up. Check your install if you only get the red LED, or it doesnt light up at all.