You can easily edit the description for your template by modifying the Description field.
1) From the template browser, select the template you want to update and click the Edit button in the top panel (or double click on the template to open it in edit mode).
2) In the editor, select the Styles tab
3) Select the Description text area field
4) Update the description of the template form
5) Save the template
Please note that if you create a template from scratch it will be named “Untitled Template” until you change it.