Let's see, you want to put a legless soldier floating in the atmosphere against a background of pink clouds observed from an airplane or space craft?
…and this is supposed to achieve what?
Give us some details, please.
Whoa! your 2nd (bottom) image is very, very different from the thumbnail shown by this forum.
That's a whole 'nother story then:
Just open both files, and drag the legless soldier from the Layer Panel to the other file, then convert it to a Smart Object, Scale it to taste, move it where you want it and choose your blending mode.
Yep, pink and green thumbnail for me as well, Station Two.. After clicking, fine. I wonder if there is some embedded profile that the forum doesn't like.
The two images are completely different. The soldier is front lit and even has flash reflected from his glasses. The tank is lit from the right with strong shadows on the left. You'll need to dodge and burn to make the lighting fit, and take out those highlights from the glasses, or use a different solder or background.
I suspect the soldier is someone you know, which is a pity because it is a really bad image to use in a composite.