if you can see the object in the preview, you can click on the cross-bars at its center and they'll change into translate axes - a set of three arrows, red, green, and blue - then you can drag w/ your mouse on the heads of those arrows to translate the crater (but not the upward pointing arrow, as far as I can tell).
if you can't see the object in the preview, make a note of your X and Z coordinates (I do this by looking in the camera tab at the camera's coordinates), and then type in those coordinates in on the crater's location parameters. then you should be able to do that final fiddly dragging-into-place that I described above.