Breeding bettas isn't easy, and taking care of the fry is harder. If you don't know what conditioning is (getting the fish ready to breed by changing temps, feeding high quality frozen/live foods which helps their bodies prepare for the production of eggs/energy for breeding/care of eggs and fry) than I think you have a lot more to read about before attempting this. They have to be introduced properly. The male needs to have an eggnest ready, or start building one pretty quick from seeing the female 'in' his area. She needs to be 'eggy'. Temp of the water needs to be right, and even after all that they may just not click, or one kills the other, or the dad doesn't care for the eggs/fry.
Also, remember you still have to get homes for all the fry you do managed to raise, so I hope you have someone lined up to sell/take them to. Most people don't care about veiltails anymore, and want the 'fancier' varieties. There are also genetics to considered that will influence colors, fins and body shape.