12-07-2013 12:45 AM
You can download the game through the Origin Client which you can download here: http://origin.com/download. Log in the client, if you've registered the games at thesims3.com, the games should already be availble for download.
If you didn't, you should be able to redeem the codes.
You will need to uninstall the disc version and get the download one so make sure it properly shows up in Origin before doing that.