How do i make chocolate marshmallow fondant?

You can add melted chocolate to the melted marshmallows and/or cocoa powder to the powdered sugar. There's a recipe here...

http://www.baking911.com/recipes/cakes/fondant_marshmallow.htm

I add 1oz. of melted chocolate per batch of MMF.

That's a great idea...thanks for the tip, I need to make chocolate football players for my brother in law's cake.