Learn good walking form. You already know how to walk, the only trick to endurance walking like this is the arm work. Bend your arms at the elbow so that you are holding your forearms parallel to the ground; lightly clench your hands. Now when you step out with your right foot, swing your left arm back. When you step left, swing back with the right arm. Keep your forearms parallel to the ground and work your arms so they are parallel to each other. Do not let your arms cross in front of your body.