If you click on any living person in your tree, one of the options in the upper left is to “Invite (name) to share family". Once you click on that, there are several ways to share your tree.
You can also choose to give them permission to edit the tree, or just to view the tree.
Note that once you share your family tree, there is no way to remove either the view or the edit permission. Even deleting the family tree will not change their ability to access it.