Templates are simply a pre-selection of Tabs and colour schemes.
You can change the selected Tabs at anytime by using the Content section.
Delete unwanted Tabs by hovering the Tab Menu and clicking the Remove from App.
This will send it to the Inactive Tabs toolbar on the right.
To add new Tabs, click on the "+ Add Tabs" button and browse through the selection of features available.
To add a Tab to your App, click "+ Add to App"
This will take you to the editor for this Tab.
Starting from Scratch
If you prefer to start again from scratch and select a new Template, simply go to the "Dashboard" Tab on the left-hand side of the page and click the "+ Create new App" button.