What Jim V said sounds right, although I can never remember the correct direction without trial and error. What is going to happen is that you have to rotate that "tit" as Jim called it, into the groove that goes cross-ways. When the tit is finally in the groove completely, the spring should help to push it out, toward the side where you used the tool. Be warned, the spring is fairly tiny and if you let it drop to a hard surface, like the floor (mine rolled off my bench), it can bounce amazingly far and be nearly impossible to find. I crawled around for an hour with a flashlight before I found mine at the other end of the garage.
Oh, and Jim V's "fiddling" is accurate as well. After you have done it once, it will seem real easy. How all of it works may not be readily apparent until after you get things apart and then you will wonder why it was ever that difficult for your first time.