I am keeping this thread open in case you need additional help beyond what I just linked you to. Use the other thread as a reference. If you have additional questions, post them here.
Short answer, if you want to run GW on OSX. You will need a window emulator, wine. http://www.winehq.org/ It works, really well infact but I don't like it.
Second option would be bootcamp. http://www.apple.com/macosx/features/bootcamp.html So basically you set aside some space on the HD then install window on it. After that your mac can dual-boot between OS and Win. Install GW on the window side and off you go.