Q: how do I install a wireless printer to my iMac that doesn't have a cd drive. It comes with a cd but I can't use it. I have tried to download the driver online but not sure what to do now...

You posted in the OS 10.3 (pre year 2000) forum instead of the OS 10.8 forum. To get answers to your question, next time post in the proper forum. See https://discussions.apple.com/index.jspa  I'll request that Apple relocate your post.

 Cheers, Tom

If you downloaded the Brother installation package just run it (with the printer switched on) and follow the instructions.

If you only downloaded the driver go back to the Brother site and download the full installer package.