I got the Sims Freeplay game and I waited a long time for it to download. It finally downloaded and now I don’t know how to open it.
I think here is an simulator as part of the developers SDK so that to run iOS Applications on a Mac , It's meant for developers to design and test their applications before installation on the device. you'll have to sign up to have a membership.
Unfortunately it sounds like you've downloaded an iOS app – one for the iPhone or iPad. iTunes lets you download these to your computer, but only for transfer to your iPhone or iPad at a later date. There is no way to play the game you have downloaded locally on your computer or Mac.
If you've got a Mac, there might be something similar on the Mac App Store, accessible by clicking the blue "A" app store icon, either in your dock or Applications folder. For both PC or Mac you could just get the full version of The Sims 3, if you haven't already?