this is how i feed most of my corals unless they have seperate mouths. i take a small cup with tank water mix my solutions in itand turn off protien skimmer.add a little bit in each corner where the powerheads are
Just direct a small amount of prepared food over the whole head- don't try to get it in the mouth. You might have to try a few food items before you get one that it really likes- mine really like mysis. As I squirt over it small pieces seem to stick to the 'hammers." Definetly turn off power heads and I usually dim all lights but actinics to keep pesky fish from trying to steal!
It takes them a little time but they do eat! A lot of people don't feed theirs at all and still keep them alive, but it is my opinion that evolution would never have given them a mouth that large if it weren't beneficial for them to eat with it!
Good luck, it's really cool to watch them eat.