Mary the Is Not Null is covered in the Access Beginner 5 course.
Take a look at the Null TechHelp until you get to the other videos.

So you are pretty much going to be using it in a query at the level you are at unless you have more experience outside of Richard's courses.

another way to do this:
In the "Data" tab of the Property sheet for the form, replace the "Record source" from MyTableT to a SQL statement selecting no Null value for example:

SELECT * from MyTableT WHERE MyField Not IsNull

Thank you both! I will try that out!