Step 3: Pack the holes with potting soil and fill the water reservoire
Then pour water through the tube until it runs out of the hole at the bottom of the box. (Note: this is another reason to have a plastic bag or some other device for catching water from the box on the ground before you start.) It takes a lot of water to fill the reservoire, so be prepared to make lots of trips to the sink. I used my tea kettle since I don't have a proper watering can, and it's really more or less the same thing.