To use this harness, first measure your dog around the body behind the front legs to pick the right size. Then put the harness over your dog's head and adjust the four slides to make it fit well. Make sure it's not too tight or too loose. When using it, check regularly to ensure it stays in place. After each use, wipe it down with a damp cloth to keep it clean. Store it in a dry place away from direct sunlight to prevent damage to the neoprene lining and reflective stripe.