If the line manager has already been set and you need to amend it, please refer to the How to Amend a Line Manager guide instead.
Whilst in the Common Tasks area for the user, click on the Set Line Manager link or click on the Set Line Manager button within the Line Manager tab.
In the popup window, Search for the Line Manager using the Filter and Search then select them. Click on OK.
The Line Manager will now be set against the user.