Under the image there are some pre-loaded tags. Hover over them and the picture will be highlighted. Click on the picture and you can add tags. Click on a tag (under the picture) and you can delete it.
In a functional application, you would only allow the adding and deleting of tags to select users while in edit mode. This script is always in edit mode for demonstration purposes. When you are done playing around, you can download the source code and play with it on your own.