Select a file (or catalog) either in the Files panel to the left, or in the explorer tab that shows after double clicking a folder.
On the right-hand side of the application is the Information Panel. At the bottom of this panel is a button labeled “Edit”, click this button.
The information panel should change to edit mode. Click the set of Stickers that you want to modify (Tags, Genres, Studios, Performers). A popup should appear
Use the arrows in the middle of the popup to add and remove Stickers. When you are done, click “OK”. When the popup closes, click the “Save” button on the right hand side at the bottom of the Information Panel