oh dear, the inevitable new-to-bettas question... nothing wrong with asking, mind you, its just that the answer is long-winded and complicated
this is the simplified version:
--read all of the pinned topics at the top of the forum about breeding bettas.
--its generally unadvisable to breed veiltail or crowntail bettas that you buy at a petstore because there's too many of those bettas being bred by farms and so hundreds of them die each day just sitting on shelves
--you only need one male and one female; they'll both need to be conditioned (fed lots of protein) for 2 weeks before each breeding attempt
--the female should be lose in the male's tank for only a couple of hours just for the actual egg-laying and then be removed to her own tank.
--betta breeding can be a very expensive hobby and is definitely time-consuming; betta fry must be fed tiny food 3 times a day and have to have pristine water conditions
--once betta fry start to fight, you will need to separate the males into jars (as many as 100!)
--it can be difficult to find homes for all of your fry, especially if you breed veiltails or bettas without known genotypes. bettas can easily produce anywhere from 50 to 500 fry in one go, so unless you are willing to cull some of them, you may have to sell them in cups at a pet store.