How do I install the Sims 2 onto my Mac?

I want to install the Sims 2 onto my Mac (yes, it is the Mac compatible version.) I have been trying to install for a few days. It says to drag the folder to my hard drive, Macintosh HD, which I am doing. I already "installed" the game. Whenever I want to play the game; it says "The Sims 2 need 1 MB of space to run" and I have much more space than that. Help, please!