During your conversation with ShadowChild near the start of the DLC, you'll receive an option to either decline or accept a sidequest to place a figurine in a bank employee's office.
Obviously, you need to accept the quest. When inside the Palisade Bank, you'll find the office on the lower left corner of the 3rd floor (as shown on the map with a marker). Just find the spot on the desk next to the computer, press the button prompt and the achievement will unlock.