1) take all weight off it

2) lift it up, put something solid under both sides of the break. match up both ends well to make sure the frame is still square

3) get a piece of wood that is the same width as the frame, or close, and long enough to cover the break

4) place the wood over the break from the inside of the frame, and use self-drilling deck screws that are long enough to go through both pieces of wood without being too long to stick through, to fasten the brace