He can play what is drawn, great. Otherwise, play moves to the next person
The player has to match the card in the discard pile either by value or color. For example, if the card is a blue 8, player must throw down a blue card or any color 8. Or the player can throw down a Wild * card. If the player doesn't have anything to match, he must pick a card from the stock pile. If he can play what is drawn, great. Otherwise, play moves to the next person.