This one is fairly simply, you have to go the "Mist Section" of the Shaded Wood, it's the right path at the fork with the bonfire. Once you're in the zone, hug the left until you can go up. You'll end up in the ruin of a round structure. Go to the pile of debris to the left and you'll be able to talk to "Head of Vengarl". Keep talking until you get a menu to buy - learn gesture - talk - leave. Select the Talk option and keep doing it until the achievement appears.
Note, if you don't know how to reach the Shaded wood you have to use the "Fragrant Branch of Yore" on Rosabeth of Melfia to remove the petrification effect and open the gate.