1) Jesus commanded his eleven disciples to go forth, and teach people (make disciples).
2) Teaching others includes providing instruction about all Jesus' teachings.
3) So the eleven disciples were to teach others how to make disciples, since the disciple-making work constitutes an important part of Jesus' teachings.
4) Therefore, all of Jesus' disciples (by imitating the original eleven to whom this commission was given) have the obligation to make disiples.
I still need to hammer out the details, but I just wanted the progression of this argument to make sense to me.