Make sure the DB's are at your shoulder's and parallel to the floor, keep the elbows pointing forward, and keep the shoulder blades down and back and out of your ears. Keep the trunk in the upright Iso-Ab position.
Take a step to the side with the trailing leg staying extended, Drive the hips back, keeping your feet, knees, and hips aligned pointing forward and not out to the side. You should feel the glutes and hamstrings of the side lunge leg, adductor of the straight trailing leg and the upperback and midsection keeping you upright.
As you push off to standing with the trailing lunge leg, press the DB's overhead and repeat with the other side.