Tap each tile you find, including the pick-ups around the map. Some pick-ups are decoys, so enter them all and the solver tells you which to leave out. Tap a placed tile to remove it.
Your tiles0/14
A winning hand is four sets of three (like 3-3-3 or 3-4-5) plus a pair. Add 14 more tiles to solve.
Skull 2 of the Skullbuster quest puts a row of Mahjong tiles on the Disco roof, with tiles missing. Enter every tile you find, including the decoys, to get a winning hand of four sets of three and a pair and see which tiles to leave out.