To add a record via a register, navigate to Privacy>Registers, and click on the relevant register. You will be presented with a list of the existing records currently stored within the register, if any. Click on Actions>Create New at the top right of the register:
Enter a name for the record, and respond to any of the other fields across the various sections or tabs within the record; you also can link to any other register records via the related items tab. (The example below shows a 'HR Recruitment' record being added to the Processing Activity Register.) Click on the green Save button, and the record will be added to the register. New records can also be added from this page by clicking the red Create New button:
How do I add Related Items via a Register?