Navigate to your Dashboard from the options at the top of the page.
Look in the "Projects" box on the left side and switch to the "Templates" tab, (all the way to the right). Double-click the template from the list that you'd like to edit or delete.
This will bring you to a new page displaying the details of the template. Just below the top white box, you'll see an edit icon that looks like a blue pencil and a delete icon that looks like an orange trashcan. Click those to edit or delete.