From a template you created or cloned from a predesigned template, hover over the image of the template and click Settings. A dialog box will open so that you can edit the name, tags, and category as desired.

If you would like to use a predesigned template, you can either Clone the template to save it under a new name or edit it and click Save As when you are finished editing. You cannot edit a predesigned template and save it under its original name.