Install the RelicHuntersZero.appx via the dev portal.
Launch Relic Hunters Zero, and you’re ready to play!
Additional notes
If the game starts in a bordered window:
Open Settings on your Xbox.
Navigate to General > TV & display options.
Go to Advanced > Video fidelity & overscan.
Disable the Apps can add a border option under Overscan border.
Pressing the Start button dims the screen slightly. Pressing it again returns the brightness to normal. This is a known issue with the GMS runner, not the game itself.