Template pages are just a page type like any other. You can create them, edit them and withdraw them (see below).
When you create a new page, the system looks for a template with the right name. If it exists, its body is used as the initial content of the new page.
More specifically, the title of a template page must match the Item label property of the Page types - Overview(s) for which it applies. That is, the template called 'Policy' is used to create new policy pages.
To use page templates
Check the system setting for the templates type. This should be in place already, but possibly isn't yet. From the System drop-down display Settings. Under Advanced, check Templates type. This should show Page Templates.
From the content drop-down, select New page and pick type, Template.
Configure the template with headings, generic text, empty tables etc.
Select the template and then choose Edit from the Content drop-down. Existing templates should be grouped under the Templates heading in the All Content menu.
It is not possible to delete a template.
Instead, view the template then from the Content drop-down, choose Withdraw page from use.