Holy forget, Gilbertus's client info is awful.
Here's what you do from the mouth of a real maccigarette:
1. Download the original folder, replace the run.bat and the haven.jar
2. Open the run.bat in textedit and add cd and the directory of the folder, in my case it was /Applications/H-H2/
3. Go into Java Preferences and drag 32-Bit Java to the first slot in the list.
4. Go into terminal and type chmod 755 and drag the run.command file to the terminal after pressing space once after 755.
5. Launch the run.command and stuff bricks.
Eh...This has probably already been asked...but, how do you install the custom clients?
If you're on a PC you download the haven.jar and launch it.
If you're on a mac you go through hell for a half-assed client that has Xray.
It's worth it though.