u can't use cheats until playboy gives u his phone for when u have to take a pic of the
gang member at the basketball court but after that u can use cheats

u get the phone after one of the first missions when you look out for roman for when lone
sharks appear and press up twice and you get to type in cheats.

u put in the codes for the cheats in the cell phone first, wen u get a cheat, an easy way
to put it in (before u bring up the phone) is up, A, up, A, and ur in the cheats menu