Save this file in the Word Startup folder. In Windows XP the default location for that folder is

C:\Documents and Settings\[User Name]\Application Data\Microsoft\Word\STARTUP

In Windows Vista and Windows 7, 8 and 10, it is

C:\Users\[User Name]\AppData\Roaming\Microsoft\Word\STARTUP

When you have done that, the tab shown below will be added to the Ribbon: