If you want to know more about this tool, go to this post "Main Scene Rig"
To download it, click Main Scene Rig Download.
To install it, follow these steps:
1. Copy the “RIG_MAIN_v003.ma” file in this path:
home/xxxx/maya/scripts
xxxx -> your user name
2. Install the Layout_Custom Shelf (Layout_Custom Shelf - Download & Install)
3. Edit the button RIG_MA
3.1 Click on the button RIG_MA with right mouse button:
3.2 Click on “EDIT”
3.3 Change the user name by your user name:
3.4 Click on Shelves Tab (in the same window)
3.5 Click on “Save All Shelves