Customize your dog tags.
There are 3 parts you can customize on your dog tags.

Template Each Chapter you complete in the campaign will unlock a new template.
Emblem Each achievement you unlock earns you a new emblem.
Title Each challenge you complete unlocks a new title.

You only need to change one part of your dog tags. Once youve done any of the above, choose Play Game -> Dog Tags from the main menu and change your template, emblem, or title to unlock this achievement.