If you have registered your game on thesims3.com, it should be available for download directly from Origin (EA's client software). Download and install Origin if necessary. From there, you should have the Sims 3 in your library, and let Origin install it.
Be cautious with playing on a laptop, don't start playing before you've bought a laptop cooler. Laptops don't like the Sims 3 much, they tend to overheat, even more if they're on battery, so don't play on battery either.