Unzip the theme you have downloaded. Upload the contents found within the upload/ folder to your sites root directory.
Once all the files have been uploaded log into your AdminCP and navigate to:
Extensions >> Theme >> Import Themes
Look for the table:
Manual Install
Here is where you can find all the themes that can manually be installed. Click on the "Install" to install a theme.
Notice: If you are upgrading your theme from using phpFox version 2.0.0rc2 you must delete the theme first on your server. The themes are located in the folder:
theme/frontend/
Do not delete the folder default, only the theme you plan on installing.
Unzip the theme you have downloaded. Upload the contents found within the upload/ folder to your sites root directory.
Once all the files have been uploaded log into your AdminCP and navigate to:
Tools >> Maintenance >> Cache Manager
Click on "Clear All" to clear your sites cache.