Try looking at my "how to make levels in MED" tutorial. It mainly applies well to older versions, but the new 6.40.5 version needs a few differences. See the section covering texturing (section 4 if I recall correctly).
"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
