So you have a new job in another city, got a P.O. Box, switching apartments or you are moving for better weather... Now you have to look into switching your mailing address. The United States Postal Service has made it very easy to change your address.
This is the link you want.
this makes it extremely easy to do when moving or getting a P.O. Box or switching apartments. Which ever the reason this is the link that you would want to use. Or you could always go in to your local post office and get a form to fill out. Which ever you are more comfortable with.