Didn't it tell you on the website you downloaded it from ? Didn't realize they'd created one already!
I have heard that is very unlikely that an inSIMinator will be created for the Sims 3, afterall the site that one used to download the original from was down for quite awhile and has changed management. The person that created the first has basically bowed out of making mods. Also the fact that someone else would have come out with one so quickly with the new game makes me wonder if it is legit, where ever you got it from.
