Click on the "Settings" tab on the left menu
Click on the Company Information inside the settings
You can see the list of units, click on one of the units
Click on the "..." icon, the right sight of the Unit you want to assign a unit manager
Choose Unit Access Management
Choose the employee name who is going to be the unit manager on this section and Save it.
***To be able to choose the employee name for the unit manager access, the employee must have this unit on his/her career page.