If you’ve noticed some of your friends “looking different” on Facebook, but you look the same ole drab of a look you’re used to on Facebook, it’s because they’ve “upgraded” to the new profile and you haven’t. There’s no simple button asking you to change your profile on your main page or navigation, but if you do want the new look, you have to visit this page:
There’s buttons in the top right corner that look like the following. You have to click on the green “upgrade” button to change your look. Unfortunately, if you don’t like the new look, I don’t think there’s a way to downgrade from it.