Note: Most rules allow claiming a tile for a Chow only from the
previous player (in your case, from Tim). Notice however that most rules also
allow claiming any tile from any player, if the tile can be used to complete the
hand and declare Out (see the example below).
Click the South Wind tile while it appears in the discard slot.
Click the Kong button.
After the tiles have been melded, you get a supplement tile from the Dead
Wall. Otherwise you could not compose a hand consisting of four sets and a
pair.