You first need to take a photo or video, then type the person's @ name over the top with the text tool. It's a little tricky if you don't already know your friend's actual Snapchat name, as there's no autofill or drop-down. It will send that person a notification that you just mentioned them, however. Further, if someone clicks on the mention in your snap, they'll go right to that person's profile page. The company confirmed it was testing the @ reply to TechCrunch, but didn't hand out any more details. The feature hasn't rolled out to everyone though: we've been able to make it work with some of our own phones at Engadget, but not everyone can create or see the mentions.