How do you learn to do circular breathing?

You cannot SING a use circular breathing - your mouth is open. But you can learn to use circular breathing for almost all wind instruments. The master bass flutist Robert Dick teaches classes in this, among many other fine professional players. This is too involved to explain in depth here, but it essentially involves the Y-branch of your nose on one portion, your mouth on the other, and they meet as they enter your lungs. While inhaling (sniffing really fast) thru your nose, you utilize the air that is trapped *above the branch* going to your mouth. You can practice first with a candle flame, or with a very small wind instrument like a recorder. Like all skills, this take TIME to control. Good luck~

Hmmmnnnn...you're putting the cart in front of the horse, aren't you? You need to get an instructor, a practice chanter, and start taking lessons. If you even have a need (and I would say the majority of those playing the pipes today don't ) you can pick circular breathing later. The circular breathing is only for the practice chanter. You don't use it on the big pipes. Many instructors don't encourage circular breathing as they teach proper tune phrasing by having you take a breath at certain points in the tune.