If you picked up a new iPhone 5s this weekend or are awaiting one in the mail, you're probably aware of Apple's new Touch ID feature, which is built into the iPhone 5s's Home button. In case you haven't yet set it up, however, here's a primer on how to do so (and when you'll have to fall back to your passcode).What is Touch ID?Touch ID is Apple's new fingerprint scanner and security system for your iPhone 5s. It's built into the Home button and reads up to five unique fingerprints. (Of course, if you feel like gaming the system, there's a work-around that lets you map more than that, but we wouldn't recommend it.) Currently, you can use Touch ID to unlock your phone and to pay for purchases with your Apple ID. Our own Jason Snell offers a more thorough explanation of the service in his
