When you start the game, you will have 3 cards in your hand. You will have 2 options, to attack 100 hp with the number on your card, or cilck on the deck to add a card to your hand. Kaiba will respond to your choice with his own. A message will appear on the top of the screen saying what his choice is. The picture thingy above the word hand, is how many cards Kaiba has in his hand.
Credits to Konami, Bandai, and cinedgm for making yugi-oh