if you work out, you can eventually lower your resting heart rate
after your body has become healthy. Your blood vessels and arteries and such get clogged, no matter how old you are. The heart needs to pump faster to overcome the friction forces caused by hardened blood vessels.
Your overall goal should be to start working out about everyday and get to a healthy weight if you are not already there. Eventually your resting heart rate will lower, but it wont happen overnight! And it will never happen if you eat crap foods!