Hello  and Welcome to the Webroot Community Forums!

 

You download the latest version of the installer

Download and installation instructions for PC, Mac, Android, and iOS.

http://www.webroot.com/us/en/products/wsa-installer-download

 

for Best Buy PC version

http://www.webroot.com/us/en/home/products/geeksquad-dl

 

Then run the installer making sure that you have your keycode to hand (that is the same one you used for the other device), insert that keycode when prompted to do so by the installer, allow the install process to finish, then REBOOT, and once they system is back you should be protected, withanother of the devices under your subscription now bing used.

---