As to your questions.
No your penis will not grow longer than it already is when you have an erection. The only way is to have surgery. Approximately one-half of the penis is located inside the body. It is attached to the pubic bone by what is known as the suspensory ligament. Lengthening is achieved by a procedure that releases the suspensory ligament where it's attached to the pubic bone, thereby allowing the penis to be advanced toward the outside of the body.
Work out and get ripped is all I can tell you. Other than that there is no way. But yeah just work out properly.