The left bottom side does not look healthy - in fact, it looks dead. How long have you had it? What are your tank parameters/lighting/etc.?
Photosynthetic corals like yours feed mostly through a symbiotic relationship with zooxanthallae algae located in its tissues. They don't require much feeding from you, if any at all. They are able to grab food (such as fish poo, free-floating eggs, etc.) from the water column with their tentacles. Most corals extend tentacles at night, which is when they usually feed. If you want to feed it, you can turn off all the flow (preferably about an hour after the lights go off). Just place a bit of food on the polyps if the tentacles aren't out (like sinking fish pellets, mysis shrimp, etc.) If the coral doesn't eat the food within 30 minutes, remove the food and turn the flow back on.