Plant the Bed
Once the wall is 8 to10 inches tall, lay out a 10-foot tarp next to it and evenly mix topsoil, compost and peat moss on the tarp. Be sure to work it over, breaking up any clumps such as the compacted peat moss. Once evenly mixed, shovel the material directly into the raised bed and fill until even with the top of the wall. Next, consult a local nursery for the proper spacing and root depth for purchased plants. Take care not to overcrowd and when in doubt plant fewer plants to allow for future growth. Also investigate companion plants, such as herbs, which may be placed around and below taller berries.
Now is also the time to apply any soil amendments such as an acidifier, in the case of blueberries and other acid-loving plants. Once the plants are in and backfilled, thoroughly water the bed. This will help any natural settling of the soil to occur. Finally, top-dress with 1 inch of mulch.