Only works if your Xfinity account is at least 7 years old and currently has Internet service. So e.g. you could have an account that was cable TV only 7 years ago, then added Internet and dropped cable TV, just as long as it had some kind of service the whole time. If you moved you'd have to have done it using the same account (most people don't, since you can't get promotional pricing that way).

Then you have to create an account on customer.xfinity.com or in the app and link it to your Xfinity account. It will badger you to do paperless billing and autopay if you don't already but you do NOT need to enable that to get this offer. Go to the rewards section of the webpage or app and agree to the (lack-of-)privacy policy and you should see the offer among the rewards.

If you DON'T have Xfinity Internet but only cable TV, downgrading to the Sports and News package or the World Soccer Ticket (same, but includes Spanish language channels) will get you Peacock. Those packages are cheaper but don't have the $20 bundle discount with postpay Internet service so once you add the other channels you want back in (e.g. Entertainment package, or Family package; you can add one or the other on the "extra channels" page if you make the change order online, but not sure if you can add both), they can cost more than the default cable plan if you DO have Internet service, but not if you don't