Fitting the Rug
Hold the rug as if you were fitting a stocking that the horse is about to "dive" into.... Make sure that the main body of the rug, and the belly piece, are both on the same side, but otherwise, you need to concentrate on the neck. If you keep the horse tied up, pass the lead rope through the neck of the rug then re-fasten it. When horses are used to the rug they won't need tying up or even holding.
Put the neck piece over your horse's nose, and then gently pull it up over his eyes. If the horse is afraid, try not to let the rug obstruct his vision any longer than necessary. Most horses relax as soon as they can see again.
Make sure that the correct bit of the neckpiece is on top (the part with the clip and elastic)
Pull the rug over the horse, leaving the belly piece for now
On the offside, bring the belly piece between the front legs, then pass the straps through the loops on the back, go back to the nearside and fasten the belly piece
Fasten the leg straps, looping one through the other as you would with a turnout rug
Hoods - you will see there are four "button holes" on the neck of the rug, just up from the clips. Open these button holes with a sharp knife. You can then put the hood on the horse, then the rug, and insert the webbing straps on the hood through the button holes; then fasten the clips. The neck piece of the rug should then be on top of the lower part of the hood. Pass the strap at the top of the rug through the loop in the hood. It's extremely rare for horses to be able to remove hoods fitted like this!