Open the wish on your wishlist, change what you want, and save. Everything's editable: name, price, link, images, notes, priority, and tags.
Steps
Open the wishlist that has the wish.
Select the wish you want to change.
Update any of its details:
Name (required)
Description and Notes for extra info
Price, plus an optional upper price
Link to the store page
Images, up to 5
Priority and Tags
Save your changes.
Good to know
There's no quantity, size, or colour field. Write a size, colour, or amount into the wish's notes or description instead. See "How do I add notes, priority, or details to a wish?"
Moving a wish to a different list happens inside this same edit form. Open the wish and set the destination list there, as covered in "How do I move a wish to another wishlist?"
Marking an item as gotten is a separate thing. The owner or a collaborator can mark a wish as fulfilled, which leaves the wish alone and just flags it as taken care of.
Editing needs Contributor access or higher on the wishlist. As a Contributor you can edit the wishes you added. See "What's the difference between Full access and Contributor?" in the Shared Wishlists collection.