Duplicate the .pspimage version of your intertwined hearts and work with the copy. Window> Duplicate
Copy each of your photos and paste into image as a new layer. Edit > Paste as New Layer. (Create a new layer for each photo.)
Use the Mover tool to move images around until they fit inside the heart just perfectly! If you Resize your photo, don't forget to uncheck "all layers".
You will probably need to trim the edges of each photo to fit inside the heart. Select the Merged layer containing the double heart frame. With the Magic Wand, click in the empty space around the hearts. Enlarge the selection to "hide" the cut edge behind the heart by going to Selections > Modify > Expand. Expand by 10 pixels.
Select the layer button for the photo on the left side Cut.
Select the layer button for the photo on the right side. Cut.
Go to Selections > Select None.
Merge all layers and export as optimized JPEG. File > Export > JPEG Optimizer
