Stretch a mason's line along the wall area to give you a straight line to work along.
Dig a hole that is 4 to 6 inches deep and 24 to 28 inches wide. Flatten the soil using a tamper.
Fill the trench with builder's sand and tamper it again. Flatten out the sand using a straight board to make it smooth.
Set the first row of blocks on the sand. Place a 4-foot level on top of the blocks. Tap the blocks with a rubber mallet to make them level.
Pound pins into the holes in the landscape blocks into the sand to hold them in place.
Place a perforated pipe behind the first row of blocks with the open ends facing towards the end of the wall. Angle the pipe so that the middle is the highest point, and the two ends are the lowest to help the water flow out of the pipe.
Lay the second course on top of the first with the stones staggered. Pound pins into the second course of blocks through the holes into the first set of blocks. Continue stacking and inserting pins until the wall is at the correct height.
Apply mason's glue to the cap stones and set them on top. Cap stones are decorative blocks also available from Home Depot that hide any holes in the blocks beneath. Back fill behind the wall with dirt.