Well, Photoshop is the 747 of image editors. You have to take the time to learn it.
So you open the two pictures. Picture 1 and Picture 2
Then use the Window menu > Arrange > 2 up vertical to see both pics.
Click on the Picture 1 Look at its' Layer panel, and drag its' layer over to picture 2 and release your mouse button.
Picture 2 should have Picture 1 added in.
That's one way to do it.