If your minecraft client version (1.7.3), is different from the latest forge version (1.6.4), it’s not going to work (at least not yet). Now here is where things differ from the video. This is going to download the latest minecraft version. Then blow everything else away in the directory. Once there drag and drop these files and folders to your desktop. This will take your to your minecraft application directory where your profile is stored (sorry, I forget to mention you will need to install minecraft on your Mac first before installing forge). Then type in exactly exactly what you see below into the textfield and hit the ‘Go’ button. Open up your ‘finder’ and click ‘Go to Folder…’ The next thing we are going to do is save your current minecraft configuration, before blowing it all away with the new minecraft forge client. To skip the adds, click the ‘*’ beside the word ‘Installer’ on the ‘1.6.4-Recommended’ and download the jar file (it will save to your downloads directory). Goto and download the ‘Installer’ for the most recent recommended version (1.6.4 at this time of writing). If not (there were a few extra things I needed to do) read on. It’s good and may give you everything you need. This was a frustrating process for me, but I finally got it.