Orange trees are generated naturally in forests and jungles. If you are using an existing world, you will only see orange trees appear in previously unexplored terrain.
Orange trees will shed oranges over time, the amount limited to no more than 8 dropped oranges underneath an orange tree at any one time. When broken, the leaf blocks of orange trees have a chance of dropping an orange.
To plant an orange tree, you simply plant orange seeds on grass or dirt, a sapling will spring out of the ground where you place the seeds.
Oranges restore 2 points of hunger and provide 0.6 nourishment points, they are also used in Fruit Salad.
Orange Juice is created by placing a single orange above a glass bottle in the crafting grid.
Orange seeds can be obtained by placing an orange into the crafting grid on its own, they can also be obtained by combining Hybrid Wheat Seeds with Pumpkin Seeds.