Need help with XBOX LIVE...plz help me?

ok i got xbox live for 1 month it ended. about a month larter i boght a new card fo a month But i cant find a way to put da code iN i tryed looking at youtube videos but there loged in to live and i cant log in cuz i dont have live cuz im trying to get it. so i cant find a way to get my sh!t to work Help me plz Its making me ***& mad