Knowing where to drill holes in steel plate?
Lay the steel plate on the concrete where you want it.  Draw a line around it.  Cut a piece of paper to the same size as the steel plate.  Place it on the concrete in the same position as the marked outline.  Locate the concrete holes by gently pressing down where you think they are (tracing paper makes this even easier).  Poke a hole through the paper at the center of each hole.  Place the paper on top of the steel plate, and mark the centers of the holes.