Grid actor & Drawing a Grid on the Mouse Cursor

I’m trying to design a simulation game where you can place construction zones using your mouse. However, having only gotten the engine yesterday, I don’t know how to do this from C++ or what the best way of doing it would be. Would anyone know the best way to create a custom grid actor (drawing a grid and making a placeable actor) and how to make a placeholder grid actor follow the mouse so I know where it’ll show up? In addition, how can I query for other actors of the same class in the whole level?

Thank you.