Purchase and equip a pin from the Otto-matic machine. This can be done in the first hour of play.
After completing the first mission inside Dr Loboto's mind, you'll arrive at the Motherlobe (Psychonauts HQ). Taking the elevator behind the reception desk, you'll enter the main hall. Have a look around this hall before heading to the classroom to find the machine you need.
The Otto-matic is a shop terminal to the side of this main hall. When you use it for the first time with
, it will run you through a short tutorial for its menus, part of which involves being given your first pin for free. Completing this menu tutorial will earn you the achievement.