The example for this one is super crappy and for that I apologize but I thought I'd post this in case you guys found cooler/better looking way to use them than I can, lol.
i. Open your colored background of your choice as the background and the image of the frames above as the foreground. Move them to your desired spot on the cover. Use the magic brush under the mask tab to get rid of the white or you can choose a preferred screen type on the transform tab. Merge when done.
ii. Upload your first preferred image as the foreground. Angle it and shrink/grow it to where it fits decently into the frame. Go to the transform tab and select another preferred screen type. I believe I used screen or darken, but use one what looks best to you. If needed, mask around the edges of the frame if they go outside of it to make it look cleaner. Merge.
iii. Repeat this until you get all of the images in the frame. Save and open in Phonto and add your title and other goodies. The font I used above was chasing embers.
Super easy; just gotta use it correctly I suppose (I suck lmfao) but I hope you enjoyed this!