I am doing my first project using FM Migratore Plat, and I have a few questions:
I am assuming that the stack I am to add to the App is the sql_yoga stack?
I have not tried to add or connect a substack outside of using the File Menu in LC. I am guessing that I open my main stack and then sql_Yoga then using the general properties set the sql_yoga stack as a substack?
I next wanted to enter the serial number for yoga into the properties on my main stack in the custom properties, but the directions did not state which part of the custom property to use?

Yes, the sql_yoga.rev file contains the libSQLYoga stack you need to add to your project. You would open the property inspector for the libSQLYoga stack and assign the mainstack property to your main stack. This will make libSQLYoga a substack of your main stack.

Instructions on unlocking SQL Yoga can be found here:

http://revolution.screenstepslive.com/s/revolution/m/sqlyoga/l/6858-unlocking-the-sql-yoga-library

You don't set any custom properties. Just make a call to a SQL Yoga command.