Take a roughly shoulder width grip. There should be a straight line from your elbow to fist (vertical forearms).
Push your head foward and press the weight toward the ceiling by extending at the elbow joint and flexing at the shoulder joint.
Press until your elbows are extended and push your head forward slightly.
Barbell Behind The Neck Seated Overhead Pressエクササイズガイド - Shouldersワークアウト | MuscleWiki