Alright to call uno you have to be able to set your cards up so you can get your hand down to one card. You want to be able to plan this so once your cards start going away you can button mash X so noone can challenge your UNO! After you call Uno get rid of your last card and *ding* achievement unlocked. Be sure that if you pick up a card after uno to recall uno everytime you go back to one card.