The Moby website has good clear pictures. The only difference I would have with the instructions is that I like to emphasize when I'm teaching the use of stretchy wraps that you should make sure your fabric is spread out and flat rather than bunched or twisted when you're putting it on. (The pictures don't show the spread clearly enough IMO). This distributes the weight across your back and ensures that you don't get a pressure point from a twist in the fabric. You can always fold up the shoulder pieces when you're done to make it less bulky over your shoulders.
I find that I get the best results when I tie it a bit tighter than I think I'll need it, and pull the slack in the shoulder pieces to the front. It's a stretchy material and gives under your baby's weight/mass when you put him in, so tying it snugly gives you the best support.
I prefer the upright, tummy to tummy position over the cradle position -- especially for a small baby like your ds -- it's easier and safer in terms of protecting his airway.