An acorn is a seed. Just like any other seeds, you plant it to get the plant you are trying to grow. Plant acorns just beneath soil surface and put up a screen to protect from Jays and squirrels. They usually sprout in about two weeks. A surer way is to look under an already grown oak tree. If the time is right, you may find already sprouted oak trees.
An acorn becomes a tree when a smurf jizzes on the plot of land you are planting the acorn on