How do you get links first clothes in wind waker?

Link doesn't have pajamas, but you probably mean his blue shirt and orange pants. To get him permanently in his regular clothes instead of the Hero's clothes, you must beat the game. When you beat the game, you can save your file and start over a second time. If you decide to play it again on the saved file, it will start you from the beginning and you can play the whole game in his regular clothes.