iWorks templates downloaded from Apple Store

After you clicked the Install button on the Mac App Store, did the acquired templates become available within the My Templates section of the Pages template chooser? Otherwise, contact the selling vendor for those templates.

Which specific templates did you get from the Mac App Store. If you scroll down on the product page, you will see on the right one above the other: A vendor name, Website, and Support links. Are these not present?

Here is what is shown for Toolbox for Pages: Templates (as an example):

Each of those are active links to the vendor site. Further down, you will see a Compatibility category. When you click on that, it may state a minimum operating system version needed to install and use the product.