You can't. There are no current acceptable surgeries or medications to lengthen the penis or increase penile girth. Although there is a surgery that some doctors will do, it is not accepted by the american urological association and has complications associated with it and is not recommended.
Look bigger! You can't actually make your penis bigger. You can make it fuller with vacuum devices and constriction bands to decrease the rate of venous outflow. Problems with this approach: not spontaneous, lack of sensation, pain. Make sure you get a quick one hand release band or else you may have to get surgical removal of your band! no metal!