Download the RBZ extension file and make note of the file location, usually this is your Downloads folder.
Install Instructions:
Login to your computer as an administrator to assure the extension files get installed into the proper locations with proper ownerships and properties.
Launch SketchUp.
Open the SketchUp Preferences control panel.
On Windows:
Window > Preferences
On OS X:
SketchUp > Preferences
Select the Extensions preference.
Click the Install Extension button.
Locate, select, and open the RBZ extension file you downloaded earlier.
Approve and acknowledge the installation verification dialog panels.
Close the SketchUp Preferences dialog panel.
The extension can now be launched from the SketchUp Extensions (formerly Plugins) menu.