You can edit hierarchy right away by drag and dropping the users from the Hierarchy builder panel to the left.
You will find a Hierarchy builder panel where you can see the list of all the active users. If you want to see only the free users(with no manager) - just put away the checkbox.
To add a user as a subordinate simply choose a person and hoover it on his's future manager.
To delete a user from the Hierarchy you need to go to the User's manager profile, open his hierarchy and click cross on the user you want to be deleted. The relation manager-employee will be removed.