How do i contact them? I brought some AC and it aint showing up?

What platform did you buy it on, XBOX, Windows 10, or Steam? If it was on XBOX or Windows 10, make sure you bought it on the account you use when playing the game. If you bought it on Steam and also play on XBOX, or vice versa, you have to log-in on the platform where you bought the AC in order to obtain it in-game.