You can edit your listing from your Zillow Rental Manager account on Zillow:
Zillow Rental Manager
Additionally, you should have a Rental Manager area of the "My Zillow" drop-down or Agent Hub drop-down when hovering over it on the top right from any Zillow page. Clicking on Listings will take you to the account.
If you do not see this section in the drop down menu, please edit your Profile and select that you "are a landlord or professional" and select Landlord. You will then have a "Rental Manager" area within the "My Zillow" menu when you hover over it. You can update your profile by clicking the link below and then selecting Edit.https://www.zillow.com/myzillow/Profile.htm
If you are on a professional profile already (you see Agent Hub instead of My Zillow), simply use the link above, edit your profile and select either "Landlord" or "Property Management" as specialties near the bottom of the page. Then Rental Manager will appear when hovering over Agent Hub.