I'm new to the site and I noticed that a game needed a rule edit, how do I edit the rules?

You can only edit the Rules if you are Mod for the Game. If you aren't, request a change to a Mod (PM him on Twitch/Twitter or on the Game Forum).

If you are a Mod, you should say that to other Mods as well and discuss it first. When everything is fine, go to the Games-Page, and click on the left side "Edit Game". Scroll down to the Categories and click into the Textbox, then edit the Text/Rules as needed. Then click the "Save Game" button and you're fine.