Adding credits to the unverified "Additional Credits" secion

How do I add a credit on the unverified "Additional Credits" section?  Actually, the credits that I am trying to add to that 'Additional Credits' section have been verified and posted on the main credit area for some time.  So, back to my original question, there is a small 'Edit' sign next to the 'Additional Credits' title so I click it then it opens another page on the right side showing the credits that are already there but no icons or instructions on how to add the new credits to the section.  Where is the instruction located and what does it say for me to follow?   I have been trying but don't see any instructions on how to add to that 'Additional Credits'.  Please let me know.  I have been a member for over 20 years.  Thank you so much!   :)