We just bought this tree this year and it has fruit already. How do I take of it?
This article will take you through the steps to having a healthy tangerine tree: https://www.gardeningknowhow.com/edible/fruits/tangerine/tangerine-tree-care.htm
Trees in their nursery pots frequently fruit. When you plant it, it will probably a couple of years before it starts bearing much fruit.