creat object
set position to x = random(scrollx, scrollx + originalwindowwidth / 2); y = random(scrolly - originalwindowheight/2, originalwindowheight))
Or if you mean the right edge of the screen for x it is not random, but just scrollx + originalwindowwidth / 2
hope I didn't make a mistake. scrollx and scrolly should be the middle of your window and half of the screen width added, you will be at the edge; for your understanding.