There's several possible issues in play here:
For Dreamweaver to properly recognize the existence of the template, the folder in the root of the site should be Templates
and not templates
.
Once Dreamweaver "sees" the Template properly you then need to make sure that the proper code is present in the child HTML files so Dreamweaver knows which files to update via the template. This code takes the form of HTML comments scattered throughout the page. You will always have the following line after the <html>
tag:
<!-- InstanceBegin template="/Templates/TemplateName.dwt" codeOutsideHTMLIsLocked="false" -->
After that, editable regions are delineated with code that will look like this:
<!-- InstanceBeginEditable name="someregion" -->
stuff you can edit
<!-- InstanceEndEditable -->
Without the above, the child pages will not respond to the template.
Now for the real bad news. Unless the existing pages match up with the template exactly, you are going to have all kinds of problems getting the template to play nicely with the existing content. Doing Modify | Template | Apply Template
to the page when the page is already fully formed will generate a dialog box that asks you map the content to the editable regions in the template. But if the rest of the design elements vary from what the template contains, Dreamweaver will preserve those tags alongside what the template will introduce which usually creates a ton of duplicated tags and broken layouts.
You would be FAR better off creating new, blank pages from the Dreamweaver Template and copy/pasting the contents into the editable area and then overwriting the "old" pages with the Save As command.