On a finding
Open the finding page.
In Actions, choose Add an action.
Choose its kind (interim, corrective or preventive), give it a title, and pick an owner and a due date. The due date starts as the finding's fix-by date.
Save.

Adding the first action to an Open finding offers to move the finding into remediation.
On a unit
Open the unit screen.
In Findings & actions, choose Add an action.
Say what it's about: one of the unit's controls, or the unit and its risk in general.
Fill in the kind, title, owner and due date (14 days from today by default), then save.
Warnings
Due after the finding's fix-by date - allowed, with a warning.
The owner can't see actions - they'll still see their own, but you're warned in case it's a mistake.