You can either go to Best Buy and pick up a membership card (I recommend the 12 month..I know it's $60, but it's better than buying a membership every three months). Once you do that, press your Xbox guide button (the silver button on your controller) and scroll all the way to the left and select redeem code. It will prompt you to put in a 25 digit code (which is located on the back of the card) and after that press the start button and there you go. Hope this helps!
Microsoft - Xbox Live 12 Month Gold Membership
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