How do i actibe the in game time codes that were posted in the guides section?

Just reset the game and enter the stage again after you added the cheats. The cheats usually don't work instantly when you add them while the game is loaded.

How do I add the codes?

Do I use something like gameshark to enter the codes?

Yes, they are Gameshark cheat codes. https://www.wikihow.com/Add-Cheats-to-Project-64

Thanks for answering my question :)