First, any new tree of whatever variety needs a minimum of 2 gallons of water per week, so you will need to keep it watered, whether its raining or not - the water needs to penetrate to the bottom of the rootball, after all. You can stop watering in late autumn, but will probably need to carry on again from early summer or late spring, depending on the weather.
Secondly, this tree will reach 80 feet eventually - it grows roughly ten feet a year, so it does it rather quickly, so you've a decision to make - if you want a tree that large, then just leave it alone. If you don't, decide whether you want to keep it as a sort of lollipop at a height you can reach, or whether you want to stool it to the ground every year and let it regrow as a shrub every time. If you decide on the small tree option, you will need to cut back the lead shoots every few weeks during the spring and summer to keep it under control.