to breed flowerhorn, it depend on what you are planning to achieve. First, you will need a proven fertile male since not all males are fertile and you will need a female but make sure the female is smaller than the male. Setup a tank with divider to divide the pair and put a clay plate on the male side. after you see the male start to clean the plate, then it meant you are in luck and try to let the female in by pulling out the divider. Keep your eyes on them to make sure there is no major fight between them, if you see they starting to fight like they both just want to kill each other, then time to divide them again. repeat this step after couple days and if that doesn't work, it time to move to plan B and find yourself a different female.
there are more about breeding flowerhorns but this is a first step so good luck