5/. Having the three images as .PNG files, it's time to bring them one, by one into the background as layers. The main background image is Layer1.
Layer 2 is going to be the "couple" image. Copy it onto the Background image. If it is too large and that's a reality.
Use the Edit/Free Transform command and using the corner toggle resize the image. An alternative is to the Transform option is the delete the layer, open the image by itself and resize using the Image Size Resize command.
Then copy/paste the image back onto the background image as Layer2.
Do the same for the other two images. With these (If you need) you can flip either/both horizontally to obtain a better effect. But you do this before copy/paste into the background as a new layer.
6/. You will also need to reduce the opacity on the three "people" images, to obtain the right sort of effect on the layer you want to first reduce the opacity and in the Layers Window, reduce the opacity by say 50% and see the effect. You may need to go higher or lower depending on the image intensity.
7/. Repeat the steps for the other two images, ensuring you first select each layer as you work on them.
8/. Finally, check the now almost complete image, in it's PSD (Photoshop editable format). If you are happy with the result, save as a .JPG (final image) file and you are done!