Uploading downloaded fonts to PS on a Mac

I've been trying to figure out how to install a downloaded font into Photoshop on my Mac. The problem is that my Mac runs on OSX, but my Photoshop is older (PS 6) so it has to run in OS 9. This isn't a problem until I try to install a font. I can't seem to install it into the right folder to make it show up in OS 9 instead of/as well as OSX. I managed it once before, and I installed two fonts, but that was such a long time ago that I have no memory of how I did it.

Does anyone have any ideas at all? Help, please! I'm going crazy only being able to use the same few fonts!