Installing new fonts is very easy. All you need to do is:
- Double-click on the font.ttf file
- Click on “Install Font”
When you double click on a font file, other than being able to install it, you’ll also see a font character preview showing the font face. This window will also let you preview any stylized versions (bold, italic, etc) of the font that are available and tell you if it’s installed or not. This is done through the Font Book app, which can also be launched separately to manage your typefaces.
Installing to Library/Fonts always works for me. So, 2 questions;
1) Have you checked Font Book to make sure they're; a) installed and b) not flagged with problems?
2) Are the fonts available in other )non-Adobe) programs (text editors and such)?
I'm not exactly sure how this happened, because I didn't see an "install" button, but I double-clicked on the font file, this brought up Font Book, and I saw that my font was there. Then I looked at Photoshop, and the font was there!