Based on your height and weight the best fit for you is the tight end position. You have the ideal size for a high school tight end.
My best advice for you is to work hard and perform very well in practice every day. In addition, what you need to do this (and every) offseason is eat healthy, exercise by doing weight lifting, and either jogging or going for a long run every day. If you do these things, you will get faster, stronger, and into better shape, which will greatly improve your chances of becoming a successful, top notch tight end in high school football, who could go on to play college football in the future.
By the way, your chances of playing college football depend on your performance in football, especially during your senior year of high school. If you perform very well in football during your final year of high school, you will greatly improve your chances of getting recruited to play for a college football program in the future. ©