When you enter cheats, you can do a few different things. Which one you use depends on what platform you are playing on and whether or not you want to use the in-game phone. When playing with a controller, the easiest way to enter cheats is to just type in the codes as you move around the world. This will automatically use the cheats. You can also hold " or " and then enter the codes if you are using a mouse and keyboard.
Use the in-game phone. This is the second main choice. Just press "up" on the d-pad to bring the phone up, and then enter one of the codes.
So this is How to get GTA5 cheat codes