Most post offices can take care of it. Some require that you make an appointment, some take walk-ins. If you go on the state department web page, you can enter your zip code and it will tell you the locations, and if they can also take the pictures. You can save time by filling out the application online, printing it out, and taking it to the post office with you.
You CAN renew online, but it's better to go to the post office to do it, because if you screw something up doing it online, it can take months to straighten out. You are more likely to have it all go smoothly if you go to a post office.