Hi there,
it's quite easy to install custom fonts in Mac OSX 10.6 (Snow Leopard). You only have to copy your font file (typically .ttf, .otf or .dfont) to the /Users/<user>/Library/Fonts directory. That's all.
source (german): http://www.myfont.de/faq.html
Enter in terminal:
Show files:
# defaults write com.apple.finder AppleShowAllFiles TRUE
# killall Finder
or flag the file as not hidden
# chflags nohidden /path/to/file.txt
Hide files:
# defaults write com.apple.finder AppleShowAllFiles FALSE
# killall Finder
or flag the file as hidden
# chflags hidden /path/to/file
First of all, you need an apple developer account which can be created for free on http://developer.apple.com. Guess what, you can't download older versions of Xcode and the iOS SDK. I always knew that apple is EVIL! They try to force you into buying their latest OS release to develop iOS applications. But if you're still using Leopard (10.5.x) you can download a working version here.
source: http://iphonesdkdev.blogspot.com/2010/04/old-versions-of-iphone-sdk.html