Watering your bonsai tree is the most important aspect of caring for your bonsai tree. Since your tree is now confined to a smaller pot with limited soil, it will rely on you as its primary source for water other than through natural rainfall.
For nearly all bonsai trees, we recommend a daily watering except during winter months. Watering your tree daily will ensure that it is hydrated adequately. Depending on the soil mix, watering daily will also help keep the soil loose and moist. Over time with heavily organic soils, the soil may harden making it very difficult for the tree's roots to breath or absorb water.
For times that your tree requires a thorough soaking, you can utilize the tub soaking method. By leaving it in a tub of water, the soil will absorb the water from the drainage holes on the bottom. After about 10-15 minutes, depending on the size of the pot, the soil will have soaked up enough water to reach the surface.
If top watering your tree, make a few passes at your tree with the hose or watering can. The first pass will loosen the soil on the surface. Some of the water will most likely flow over. The 2nd pass will soak deeper into the soil and the 3rd pass will make sure it goes down through to the bottom of the pot.