Untwist the old spring's end from the chain and separate the two pieces. Use a pliers to bend the spring, if necessary, but be careful not to damage the chain. The spring now hangs from the header jamb by a duplex nail.
Grasp the duplex nail's head with a pliers or vise grips. Pull the nail out of the jamb.
Twist one end of the new closer spring through the lowest-hanging chain link. Locate the lowest-hanging chain link with the storm door closed.
Lift the spring's free end up to the header jamb. Position the spring about 2 to 3 inches over from the side jamb. Do not simply reuse the hole from the first spring because this won't supply a secure hold. Use a duplex nail to secure the spring in place.