You must download a Crossfire client if you want to play the game. Crossfire is a "massively multiplayer online role-playing game," or MMORPG. To connect to the Crossfire servers, you need the appropriate program. Once installed, the program will allow you to play Crossfire from your Mac. You can download the Mac client for Crossfire from the Crossfire website.
Video of the Day

Step
Navigate to the Crossfire website (see References).
Step
Click "Download" next to the "GTK Client, Mac OS X - X11."
Step
Click the "Crossfire" link under the "Mac OS X X11" binaries.
Step
Double-click the archive once it has finished downloading.
Step
Double-click the included Unix file. This will open in terminal and complete the setup.