Hey @DC_knights11! Welcome to the forums!
Yeah, it looks like you’ve got some reference issues here.
You are not assigning your “Game Object” variable- you can’t just have it named and it know exactly what thing in the level to use, what if you had 10 of those in the level? variables have to have defaults assigned, and there are ways to go about that.
As far as casting goes, think of casting as “Be more specific with this object” not “tell a thing to listen”. It’s re-molding, not a communication device. 
I suggest you do a few hands-on tutorials to get into the swing of things. This one comes pretty highly recommended, I pass this one around and I’ve yet to hear anything bad back about it- it covers a lot of bases.