I have used Photoshop to edit images for a number of years, but have not ever used it to embed images in pre-created print templates. I would be grateful for any advice you have for me -- thanks!
All templates are not created the same way. How one populates a template depends on the template document. Some are stored as PSD file some as a PNG file. So some are layer and other not. Image are added as layers using features like place, paste, duplicate layer from one document to an other. Image layers are re-sized using a layer transform and are often masked to the area being populated. Mask are also used to blend in images to create interesting composites.