There are instructions posted when you create your Forum Runner account at
http://www.forumrunner.net.
If you have any questions, email
support@forumrunner.net.
Short version:
Download the add-on, unzip it into your main forum directory (it will create a directory 'forumrunner' underneath it where all the files are).
Go into vBulletin Control Panel, Product Manager, import new product. Import file './forumruner/product-forumrunner.xml' (make sure 'Overwrite' is set to Yes).
After that, create account at
http://www.forumrunner.net/?p=register to register your forum in the directory.
once that's done, you're good to go!