To edit or copy a template's files with the Template Manager: Customise Template you must first access the Template manager.
You will now see the Template Manager screen.
Note: If you do not see Template Manager listed as an option on the Extensions menu, then it is most likely because you are not logged in as a Super Administrator. Only Super Administrators will see this menu item.
There are two methods available for accessing the Template Manager: Customise Template. The Customise Template interface allows for editing the actual code found in the template files, creating template overrides and template file manipulation.
Styles column refers to changing the available parameters of a template, such as color, font-color, logo, etc. These are dependent on the parameters a template maker made available and are a convenience for quick changes. Template - column refers to editing the actual template files.
To access the Template Customise feature:
You should now be looking at the image below, Template Manager: Customise Template.