How to use Houdini with SCID on Mac OS? I have recently moved to a Mac. Immediately I've installed Scid (looks very nice on the Mac) but I couldn't find a way to use my Houdini as a chess engine.

Supposedly, it should run with Wine, but I don't know how to do it. I understand that you have done so, so could you give me some guidance?
Although I know you're on a Mac and I don't know what you've tried so far in detail, this scid-users mailing list thread might be of interest. It suggests to add the exe file in as the command, but without the wine before it. Again, that is for Ubuntu, but maybe it will help.