Working with parent pages and subpages

I have been working with Indd for over ten years. Very familiar with using Master Pages (Now Parent pages).

I have just purchased an Indd template from Adobe stock. This template is set up to use one Master page  in addition to  a number of "Subpages." 

Can anyone point me to:

1. a source of info for working with subpages
2. any useful guides for working with templar=tes such as this?

Thank you

Mike