Condition the fishes by putting them together in a tank but separating them using anything possible so that they can only see each other but unable to touch each other. This is to allow them to get used to each other first before mating them.
Your male Betta fish will tell you when he is ready mate as he will make a bubble nest at the top of his tank where he will eventually place the eggs. The female can also give signs by developing vertical stripes on her body. 
Before putting the fishes together, feed them with lots of live food(better for them) cause they have to stay without food during the spawning season.(This is not necessary but it's for the best.) This method is preferred cause the male has to get used to going on without food during the spawning period, if not when he is used for the next breeding, he would eat up the eggs when he is hungry. Also, remember to add Blackwater or Ketapang water into the tank so that the bubble nest would not burst so easily.
Soak the Ketapang leaves in a jar of water for about a day to obtain the Ketapang water.
The Ketapang water would turn out like this after a day of soaking. Pour a little of the Ketapang water into your fish tank.
When you put the fishes together, it's normal for the male to chase and bite the female so you don't have to worry, unless the situation gets too agressive, remove the female temporary and try putting them together again in a while. 
After you have put them together the female will release her eggs, she can release hundreds to thousands of eggs. When she is done she will hide and the male will take over and take care of the young. At this time it is best to take the female out of tank as the male might fight her.
The yellow stuff in the bubble are the eggs .
This is a Thai Betta fish net, used to catch Bettas so that the finage of the fish would not be torn. This is optional, catching them with hand is also acceptable.
You may remove the male 3 days after eggs hatched(This is when you will be able to see the little fries swimming around). After the first two weeks as you begin to change the water you should also start separating the young Betta fish into other tanks. Feed the fries with Baby Brine Shrimp or a little of boiled crashed egg yolk when they are around 3 days old.
These are just our personal tips, bro&sis Please kindly correct us if you think we're wrong anywhere . Thanks (:
