Rule of thumb - don't plant any tree or shrub deeper than the level of soil in the pot.
Dig a hole about as deep as the pot is tall and about twice as wide as the pot.
It is helpful for the roots if you loosen the dirt on the sides of the hole by making cuts into the sides with your shovel.
Take the pot of your plant and stick the plant into the hole.
Fill in the sides of the hole with loose soil and pack into all in.
You can put a tiny layer of soil on top of the roots to help pack everything in but again the soil should be no higher than it was in the pot or the trunk will rot.