Lina, you need to remove the male too when all the fry start to swim horizontally. You did good though to get any fertile eggs at all.
You need to introduce the male and female to each other in a way that they are seperated and can't get at each other. That can eliminate alot of damage they can do to each other as they become aquainted. I have done this by using a hurricane lamp in a 10 gallon...female in the lamp, male in the tank. Plenty of room for both to swim around comfortabley. There should also be plenty of things..plants caves and such..for the female to hide in to get away from the male if she needs to.
Once they breed, the female is removed and you remove the male after the eggs hatch and the fry become free swimming. The water temps should be at least 80 and you need to keep the water the fry are in very clean. They don't need to eat until they start swimming horizontally, as they have a yoke sack attached to them that will last 2-3 days. Feed them infusoria at first. YOu get this by rinsing off a lettuce leaf and floating it in dechlorinated water. AFter a few days you notice a cloudy substance in the water, that's the infusoria. If you have a flashlight shining on one end of the bowl the little buggers will congregate in the lighted area and you can syphon that out and give it to the fry. It helps to have alot of live plants such as java moss in the tank with the fry because there will be all sorts of little live things on it that they can eat too. After the first week you can begin feeding them baby brine shrimp.
Go from there Lina...and do lots of online research for more info. There are plenty of betta sites that can give you even more information than I gave you here.
Good luck...but be sure you know what your getting yourself into...lol.... <img src="/images/graemlins/wink.gif" alt="" />
