With smaller pets, you will need to raise the pet’s rear, slide each leg through the individual leg rings, and then fasten the strap over the shoulders.
With large pets, as long as they don’t have bad knees, you can try the following method, which is sometimes easier than lifting your dog under its abdomen. First, see if you can get your pet to stand on all four legs, if even for a moment. Then, as you stand alongside, lean over your pet, place one hand in front of each knee and, keeping the legs straight, guide the rear legs down through the rings. This prevents your pet from pulling its legs up and getting caught in the rings. Lifting your pet this way has the advantage of not needing as much strength as you would if lifting it under the abdomen. However, if your dog is totally paralyzed, and is unable to stand on all four legs for even a moment, it is difficult to lift your pet this way.