Others, especially Joe Carroll, can give you a more accurate description, but the usual process is to fully wind the spring, unwind it one turn, attach the cord, and let the spring fully unwind, coiling cord onto the reel as it does so. Then pull the cord out about three inches, cut it, and tie on the T-handle. The idea is to end up with the spring a few cord-inches away from fully extended, when you've pulled out all of the cord.