As in block or brick laying, courses should be staggered for extra strength. This means the second course corner can be made from two panels...one panel cut in half. This creates panel A and B. Place the left half, panel A in position by sliding it down the guide of the corner support.

Cut 1/2" off the left side of panel B and place it in position. Take a new panel and cut 32" off the left side to creat panel C. Place panel C in position across from panel B. Cut 1/2" off the right side of the remaining piece to create panel C and place it across from panel D.

Be sure as you move up the wall that alternate courses are staggered.
Once the block level has reached grade it is a good idea to note the position and dimensions of all openings in permanent marker.