Ah, for knowing where things are, just open the file you want to put the grass on to, save it under the grass name you want as a temporary file, then, from that, just put the grass where you need it then deleting the ground for the main file to be used.
"You level up the fastest and easiest if you do things at your own level and no higher or lower" - useful tip
My 2D game - release on Jun 13th; My tutorials