If you are doing the MotoSkills, you will unlock this achievement on MotoSkill 6, which teaches you how to pull freestyle tricks. The first trick you are told to do is a Shaolin. Just hold LB and move the right analog stick up, down, up. After successfully landing, you will unlock this.
If you did not do the MotoSkills, just enter into any event, (easier during freestyle) and hold LB and move the right stick in three directions while in the air. After landing, this achievement will unlock.