The are two kind of pins. Type I pins are more difficult to print. They should be printed vertically. Type II pins are easier to prints (are the recommended pins) Once the pins have been printed, just push them against the servo holes and the part you want to attache. You should hear a click sound More information (in Spanish) in the github repo: https://github.com/Obijuan/3D-parts/wiki/Servo-pins-para-Futaba-3003