Traditionally, to install new fonts into Photoshop or any other application you would go to the Windows Control Panel and drag and drop the files into the Fonts folder.

The only downside to installing fonts into Windows itself is the fact that the more you install the slower Windows becomes.

If you intend to only use your custom fonts in Photoshop you can install them by going to:

C:\Program Files\Common Files\Adobe\Fonts

Drag and drop the font files into the folder and the next time you start up Photoshop they should be in there.

There is still a caveat here because if you install a large number of fonts into Photoshop, it will take a longer time to load Photoshop