do you reaseach google betta fry care or somthing basicly all i can tell you is the better the water quality the better luck you'll have and feed like 4-5x aday of the right foods ex. microworms bbs
Many bettas can produce hundreds of fry, so you have to plan out wether you have the tanks, space and a good local fish store that will accept them before you attempt to breed bettas as you could end up in a tricky situation with no where for the fry to go to when they have grown up