Assignment of control institutions
The assignment of control institutions to project partners is performed in a dedicated page. There is a dedicated privilege to this page:

The assignment page shows all partners (including Inactive ones) of projects with the status Approved (or any later stage):

The assignment is simply done by selecting (drop-down) the right Institution for the corresponding partner.
Only institutions with the same or wider geographical area (NUTS) than the partner are shown.
The partner geographical area is derived from the Application Form → section B.1.2 Partner Address

When the partner address is not filled, the system allows the assignment of any control institution.
All controller users of an institution can have access to the project as soon as an assignment is done. All users who have access to Application → Project privileges can also see the respective assignments:

An assignment can possibly get broken on two different scenarios:
The project went through an AF modification where partner address is changed
The privileged user changes the geographical area of an existing (and assigned) control institution
The system is aware of such scenarios - If the change of the geographical area still complies with the jurisdiction of the control institution, the existing assignment persist. If not, the control institution assignment is dropped and manual assignment of a new control institution is required.