As for guiding you through it, first and foremost, bettas do not belong in a bowl. They need a heated, filtered tank, minimum size 5 USG.
I realize many people in the past have kept bettas in bowls/vases/etc, but it really is not good for them, and many consider it cruel to limit them to such a tiny space....and when that tiny space is not filtered (or heavily planted), the fish is basically living in it's own toilet, to be perfectly honest.
Please consider getting the fish a real filtered and heated tank, of the proper size.