Sims 3 Mac Downloading issues

I have been trying to download Sims 3 for a week now and I cannot figure it out. Ive watched videos and tried the step by step instructions. I have changed rar to dmg and it still is giving me issues. If anyone is bored and would be kind enough to do team viewer to help me I would love it.

UPDATE:
I was finally able to install the Sims 3 but when I try to play the game it says You are playing a non-final, unathorized copy of The Sims 3.
How do I fix this error? I'd love it if someone could help me.

What kind of issues are you getting?

Once I try to download the sims 3 it says "could not verify the integrity of the installer" I dont know what to do.

I would uninstall the game including expansions using my favorite mac software tool AppCleaner! Appcleaner will grab all of those pesky extra files that are left from the install. Please follow these instructions here and when you go to install the Expansions you MUST install them in release order. If you have anymore problems please drop me a line and I will help you out to the best of my ability! Happy Simming!