This illustrates what it looks like when you have drawn a tile (the 3 of Sticks) that can make a Kong. The interface would look similar if the tile had been discarded by another player, except that the large tile would be in the discard area.

The green button will accept the tile to meld the Kong and a replacement tile will be drawn.

The red button will reject the tile and play will continue immediately. In this case, since it was Player's draw, it would be time for Player to discard.