(From the prostores KB)

Here is a code snippet that will insert your custom page title on certain pages and then use the default ProStores functionality (the product name, category name or template name used for page title) on any pages that do not have a custom page title defined.

On the Header template, replace the default code:

With code like this: Title Code

And then add the directive code to the top of the page for any the targeted body templates (storefront, about, service, etc.) where you want a customized page title. You would edit the content in the tag (red text section) accordingly for each template you want updated.