How large is your tank? Difficult to tell from a pic, but I would guess about 40g? How many Firemouths did you get? What are your water parameters?
Firemouths are actually easy fish to care for. They'll thrive perfectly well on standard cichlid pellets like Hikari Cichlid Gold. They also like a treat now and then, and are especially fond of frozen blood worms, brine shrimp, or tiny krill. Apiece of dried seaweed or finely chopped spinach a couple times per week would be good also.
They appreciate caves and hides, though they won't spend as much time in them as most African cichlids do.
I read and hear often that they make good community fish, but I disagree. They're too aggressive for most community tanks, and can hold their own with oscars and Jack Dempsey's just fine. Most of their overt aggression is conspecific however.
I don't know what else to tell you, but if you have a specific question, I'm sure someone will be able to answer it here.