since this is your first grow I would have strongly suggested starting it off in a smaller pot. Most first time growers tend to over water their plants. In a 5gal pot it's very easy to over water a small plant. Since the roots aren't in most of it, the water will just sit towards the bottom of cause your soil to turn to sludge, which in turn can cause root rot.
Usually you don't want to water directly on the stem of the plant, but since it's a seedling in such a big area, I would only water directly under the plant. You can tell when a plant needs water because the leafs will start to get droopy. Another way to tell when to water (the best way in my opinion) is to wait until you see the plants start to droop (so you know it's really dried out) and pick up the pot and feel how much it weighs, Now water it until you have a little run off and pick the pot up and feel it's weight. Now you now how heavy it feels when it's thirsty and when it's watered. I would stick with waiting for it to droop this time, next time start off in smaller pots until you get the hang of watering.