As the snake has shed part of the head, now is the time to assist him out of the rest of the old skin. Mostly the following procedure involves patience and gentle handling. The only materials needed are your hands, a towel, and a soaking box.
You need a plastic shoe box or something similar to soak the snake. Use water approximately 85 degrees Fahrenheit (roughly 30C). Use enough water to reach 1/4 of the way from the snake's belly to its backbone. About every five minutes pour a little water over the top of the head. After about 30 minutes try to loosen the skin around the lips, either the upper or lower jaw, with a thumbnail. Get the skin off as much of the head as possible. For the retained eye cap, place your wet thumb on the eye cap and wipe towards the rear of the eye. The friction ridges of the thumbprint will probably pull the eye cap back far enough to get it off. If the eye cap does not come off, it is no big deal. Leave it to come off with the next shed. One the shed skin is off the head, it is mostly a matter of letting the snake crawl through a wet towel, turning the old skin inside out as it goes. Make sure the skin on the tip of the tail comes off.
Good luck.