How do you add circuit breakers to a 200 amp panel that is already full?

You can buy what are called Tandem circuit breakers. These only take up one space but allow you to connect 2 individual circuits to it. For example, say you had 4 - Single pole 20 amp breakers taking up 4 spaces. You could buy 2 - 20 amp Tandem circuit breakers and that would give you 2 additional spaces in your electrical panel. Just add up all your amps that your circuits will be pulling at one time to make sure you won't be overloading your electrical panel. One drawback to these Tandem breakers is that they are rough on your wallet. They are pretty expensive compared to regular breakers. Hope this helps