Now flip the whole thing over onto the legs.

Take the two 52 1/2" 1X4's and attach one to either side of the stand about 8 inches from the bottom.  (The original instructions said about halfway up which would be a little over 10 inches but later the instructions said to use the 9 inch pieces for legs at the front of this part of the frame.)  These additional pieces will form the step and add extra support.

Now add the two 16 1/4" pieces to the ends of the 52 1/2 inch 1X4's to finish framing the step.