Editing a Single Asset in the Asset Library
Whilst you can't edit image files after they are loaded into the asset library, you can edit the searchable asset data related to that asset. We call this the asset metadata.
To edit your asset metadata for a single asset in the asset library, head to your Asset Library.
Click on the item you'd like to edit. Then click Edit Metadata. If there's more than one item in the asset overview on the left side of the page, you'll also see an option to batch edit your items. Check out this guide for more information on batch editing.
From the resulting page, you'll be able to edit the searchable terms for your asset. Once you're happy with your changes, click Save.