Howdy hfevrier,
It sounds like you would like to add fonts to your Mac. You can use the Font Book application to preview and install additional fonts. This article should help you do that:
Mac Basics: Font Book
http://support.apple.com/kb/ht2509
Preview and install fonts
To preview a new font that you downloaded or have on a disc, double-click the font file. Font Book will display a sample of the font. You can change the typeface (if others are available) via the pop-up menu at the top of the preview window.
If you want to install the font so that it can be used in documents you create or view, click the "Install Font" button that appears below the preview of the font.

You can also use Font Book to install one or more fonts. Choose Add Fonts from the File menu, select the font or a folder containing multiple fonts, then click Open to install the font(s).
When Font Book installs a font, it will automatically validate the font and let you know if it detects any issue with the font file. See the "Validating fonts" section in this article for more information.
By default, Font Book will install fonts in a location where the font will only be available to the current user account. If you'd prefer to install fonts in a location where they will be available to all users on the computer, choose Font Book > Preferences, then choose "Computer" from the "Default Install Location" pop-up menu.
Thank you for using Apple Support Communities.
Cheers,
Sterling