When you purchase the MBS plug-in you will receive an email that contains all of your registration information. To register the plug-in you just need use the MBS Register function like this:
MBS( "Register" ; Licensee Name; component; License Type; Expire Month; Serial number )
You can use this function anywhere that you can create a FileMaker calculation, but most often people place it in the startup script of a solution. That way the plug-in will be registered when the solution starts up. You only need to call this function one time for each FileMaker session.
Take a look at the example file below. It shows you exactly how to set this up.
Note that the when you launch it the first time it a dialog appears saying that the plug-in was not registered correctly. This is because you have to enter your license information into the register script first.
MBS FileMaker tutorial videos