Clean the surface of the brick with Krud Kutter & a rag.
Prime the brick using Zinsser primer with at least 2 coats.
Paint the fireplace cover with a high heat paint made for metal.
Paint the primed brick with your latex paint, and do 2-3 coats.
Cut & stain your wood pieces and assemble them on top of your fireplace using a nailgun to create a mantle. Then seal with polycrylic.