Is the file you downloaded still a .zip file, without an unzipped version visible on your Mac? In other words, did your Mac not automatically unzip the file?
If that's the case you can manually unzip it using Stuffit Expander. You can download a free version at http://www.stuffit.com/mac-expander.html.
If that's the case you can manually unzip it using Stuffit Expander. You can download a free version at http://www.stuffit.com/mac-expander.html.