How do you do the motherlode cheat?

I just got a MacBook today, and my first thing was to download the sims lol. My freind has the game and always uses the "motherlode" cheat, but I can't seem to get into the cheat catagory. I know you have to tap on shift command and c, but whenever I click c it always takes a screenshot instead of bringing me to the cheat screen. Can anyone help??