They need a small (not tiny) bowl or tank with minimal water flow. Feed 2x/day small amounts and change 25% water weekly. Don't mix with other long finned fish.
Betta fish require very little water circulation. It has something to do with their gills or maybe their metabolism. Any way. I have found that even though they don't need too much circulation, it is easier to maintain a tank with a large volume (your chemistry is more forgiving). Most importantly you shouldn't fight them that is cruel.