How to use font installed without rebooting the system?
You should not try to install fonts by copying them to the /Library/Fonts folder. This may cause problems.

To install fonts start the FontBook app (Applications/Utilities) and use the command Add Font … in the File menu . This will activate the new font(s) and you can use them immediately without a reboot. This procedure is useful if you want to install several fonts at the same time.
If you only want to install one or two fonts, you can double click on the font(s) and click the Install button in the preview window of Font Book.

In FontBook you can also activate, deactivate or delete fonts, group them, etc. 

Once you add the font to FontBook, you'll need to quit the app you are using (like Pages) and reopen it; at that point, the font will show up.