Dynamic Template Switcher (DTS) allows both admins and users to determine templates of choice to be applied.
On the DynamicTemplateSwitcher module on the left side bar of the site, select any template and select 'Preview' and click on the submit button. You will be able to see what the template looks like.
Select another template and select 'Preview'. The template will be viewed.
Now login to the site with username: demo and password: demo123. Select a template you would like to apply and select 'Save'. Click on the submit button. This template will be applied every time you are logged in to the system.
Logout from the system, the template will go back to the original template assigned by the admin.