Need help finding a specific folder for a friend
Most likely ~/Library/Application Support/Cockatrice


~ denotes the user's home directory. This should exist in their sidebar already, labeled with their name.
Library is hidden on Mac OS X Lion and above. The easiest way is have the Finder active, hold the option key (⌥) and click the 'Go' menu. This will reveal the 'Library' folder that you can select.


The rest of the paths should be able to be accessed normally.