To cut out a pocket around the outside of the logo, you would draw two rectangles, create a Pocket operation, and assign the two rectangles to that operation.
You may be looking for vcarving - this feature isn’t yet available in MillMage, but when we release MillMage Pro in the near future, it will be - you can see development of those features here: Relief Carving - Work in Progress
I’d strongly recommend that any new user like yourself start with the guides we have in our documentation here: Project Setup Wizard: Beginner - MillMage Documentation