Qt Colleague's on a more senior level-(compared to me(beginning)

I want to load 2 Images in the same label
My Program entails:
(spot the difference Game)
Once a user clicks a point on 1 image & a corresponding point in the next image
a line must be drawn between them.
If I load the image in 2 separate labels, i'm not sure how I would draw a line between them accordingly, Though
If I do load the images in separate labels, it will be easier to get coordinates to test if points match!

pro's & cons...

Ideas on how to approach this problem?
link to an example, maybe
Help appreciated