To assign a currently unassigned user to a node in the hierarchy:
From the Tasks section of the navigation bar choose Hierarchy. The Hierarchy screen opens.
Select the Unassigned Users tab in the Details panel. If you do not see this tab, there are currently no unassigned users.
Select the user you want to assign from the list, or search for them using the Search field.
If you want to assign more than one unassigned user, press and hold the
Ctrlkey and click each of the users you want to assign. Users can be assigned to more than one node if the multi-user hierarchy feature is enabled.
Use your left mouse button to click-and-drag your user selection to a node in the hierarchy tree in the left panel.