To edit or delete tags, go to the Users section and click on the manage tags icon.
From there, you may either Edit, Delete an existing Tag or create a new one using the New Tag button.
By default, tags are in alphabetical order but you can sort them by count as well (to do so, simply click on "Users")
Deleting a tag will remove it from all associated users. That action cannot be undone, so be careful before deleting a tag.