Playing Sims Medieval without CD drive

Hi, I bought the Sims Medieval a while ago, and just found this game again and want to play it. Unfortunately, my modern mac doesn't have a CD drive. I have an external DVD writer, and I was able to install the game using this, but it won't let me actually play it. I even did a chat with an EA support person, who told me to download origin, and when I did he added the game to my library. Except now, it won't play in Origin because every time I try to download it there is always an error message saying that it failed to download.