João Cardoso, I can not do this at the same level of detail as the instructions that are already on the referred page. If you have the time, please put the instructions for Mac users.

Windows Phone 8 development on a Mac running OSX and VMWare, using also the phone emulator:

What is needed is a more recent Mac (MBP Early 2011, i7 in my case, OS X 10.7.5, 16GBytes RAM), VMware...