1. Open the cheat Bar
First you have to use Shift + Ctrl + C at the same time to open the cheats bar. It appears as an empty text space at the top of the screen.
2. Use your awesome cheats
Then you can type in any cheat you have Googled or heard about and press enter to get the results. I personally love the "Motherlode" cheat as it gives your family 50000 Simoleons without needing to work.
Bonus
The cheats seem to work on all Sims variants so if you dont have the latest Sims 4 you can still use it!