Every time you figure out where all the buttons are on Facebook, they move them! Several people have switched to the new timeline and are having a hard time finding the “protect your page” link to authenticate their page.
It’s located on the easy-to-miss little “settings” gearbox on your page. See this screenshot to see where it’s located:
If you’re a page admin, you’ll see the little gearbox just to the far right of the “liked” button. (I’m assuming you’ve “liked” your page if you’re an admin.)
If you do NOT see the “protect your page” option in that dropdown, then your page is either already authenticated, or you don’t have the option to authenticate it. You can try adding a map to your page (under location settings), to make it a “place,”which sometimes will make the “protect your page” option appear.
I keep looking for other methods; if I find any, I will definitely post here!