Welcome to the forum Kittencat :)
What you have isn't really good for him. He's probably sitting at the bottom of his bowl because he is cold. Bettas are tropical fish so they need warm water and clean water so their fins stay in good shape and they are healthy.
THose little bowls make it hard to do that. It's probably only 1/2 a gallon right? Well, tiny tanks like that need to be cleaned at least once a day. Fish release ammonia through their gills as they breathe, so in such tiny places, it builds up quickly.
I advise you return the bowl, and buy a better tank. 2.5 gallon tanks or larger tend to be easier to keep clean and warm. I know for a fact that walmart sells a five gallon kit (tank, hood, and filter) for thirty something dollars, and this tank for thirty http://www.walmart.com/ip/Hawkeye-5-...arium/14660258
In a five gallon tank, you have more room to decorate and give him a place to hide if he wants, and finding good heaters for a tank that size will be easier too. Plus, you're water changes would be much smaller water changes because of the larger size.
Heaters are a must. A good quality heater like this : http://www.petsmart.com/product/inde...ductId=2754055
is great. The company actually stands by this product for life, so if it ever breaks, you can be sent a new one.
Hiding places are always good for your betta, they keep him feeling happy and safe. It really doesn't matter what it is, it could even be a clean mug in a tank.
If you're short on money, there are other alternatives. Walmart or target sells sterlite or tubbermaid tubs, some of which are about two gallons, which would do. They're not that much, and they can be safely heated.
With the proper care your betta will be more active, happy, colorful, etc. Bettas are awesome fish, they've got personality, they're smart, forgiving of beginner mistakes, and they're addicting :)