To feed this coral turn off the pumps for a few minutes and place the mysis or other food right on the brain. After trying this a few times you should be able to see where the mouths are and I always try to feed each mouth on my LPS. Give the brain a few minutes to eat and then turn the flow back on.
Feeding is not absolutely necessary, but it will help the brain grow faster. Feeding LPS is one of my favorite things to watch in my tank as well. Good luck.