Open the control and go to Links. Two lists sit on the tab: items that already point at this control, and the catalog requirements you assign to it.
Risks, non-conformities, and improvements
The top list shows risks, NCs, and OFIs linked through this control’s ID, with a count of each. Manage risks & NCs and Manage OFIs change those links. Nothing is listed until something references the control.
Catalog requirements
Choose a framework, choose a published catalog requirement, and use Assign. The table shows the framework, the requirement ID, and the title. Click a row to open that requirement. Remove an assignment from the row when this control should no longer cover it.
Coverage on the register counts a statement as covered when at least one implemented control is linked to it. Assigning the requirement is that link. A statement with several controls is still one covered statement.