On Xbox it’s simple to use xboxdvr.com. Your clips are automatically uploaded here and you just need to copy and paste the URL.
For reporting cheating, reporting in game is your best option. If you are no longer able to or want to include a video, you can find a report contact form at the bottom of this article. Please take note of the rules listed before using this option.
https://www.bungie.net/en/Help/Article/12960