What kind of image is it? Is it a photo, or a vector drawing, or other kind of raster image?
Without knowing more details, I would say just select it and use the arrow keys. One press of any arrow keys moves the selection by 2 px. Shift + arrow moves by 10 times the step (which is 2 px by default, but can be changed). Alt + arrow key moves by.....I can't remember, but I think it's 0.2 px.
So
- duplicate
- up arrow key
- right arrow key
Or also use Shift or Alt as needed. Then repeat.