Winners are selected via raffle weekly on Friday. Once you play the raffle (See article, How do I participate in the weekly raffle?), winners will see a "Congratulations!" message appear on the screen.
Tapping on the yellow "You won!" button will take you through the steps to claim your gift. Please note your phone needs to be connected to a cellular or wifi connection in order to claim your gift.
You may also find the following article helpful, Can I chose my gift?