Keeping your listing up-to-date is very quick and easy. Firstly, head over to your User Dashboard > My Listings.
Here you will see a list of all your listings.
Select "Edit" on the listing of your choice.
You will be taken to the edit form which will show all the possible fields available to you. Simply work your from top-to-bottom and update/edit the fields.
When finished click the Save Changes button located at the very bottom.
Once the page refreshes you will be presented with a small message:
Your changes have been saved. View →
Click this to be taken to your page to see the changes.