How to move images to position in a canvas

did you try that tool that has a icon like a cross? if you double click the icon ta dialogue pop up, with option to use on the active layer . Anyway after you copy&paste you get not a new layer but something called "floating selection" to have that on its layer you must add a new layer. If you instead "anchor" that "floating selection", that will be merged with the image below and not more movable (if not reverting that step with UNdo, if image was not closed )