You should take several steps to grow moss on driftwood in your aquarium, including choosing the right driftwood, providing the right lighting, and keeping up with regular maintenance. Ideally, you will want to use driftwood that is free of any rough edges or rough surfaces, and ensure it will fit your tank correctly. Attach your moss appropriately with thread or glue and position the driftwood where it will get an appropriate amount of light. Moss will naturally attach itself and grow without any real need for intervention.