Looked all over and can't find an Answer.

Since you're not a moderator of a game, you will have to ask the mod(s) of the game you're looking to add a catagory for.

Okay, but how would one contact a mod of the game I'm looking to add a category for?

Go in the game page, check who is mod on the left side. Click on his speedrun.com profile page. Finaly, aim for networks to contact him.

Okay, thanks PackSciences and Ozotuh for your help.