82 is really not a problem for bettas. Do you have fish in the tank? If so, do they seem okay? The big problem for fish is quick changes in temp. Most tropical fish can survive in 86+. However, if the fish has an underlying illness the temp could be deadly.
For ways to cool the tank down, should you need to do so:
Turn the light off. Unless you have live plants, a light is only needed for you to view the fish. So turn it on when you want to look at them/feed them.
If you have live plants, or turning off the lights isn't enough, you can float a plastic bag with an ice cube or two in it. Once again, you don't want to change the temp fast. Because you probably don't dechlorinate your ice cubes, make sure the water doesn't get in the tank with your fish.
And welcome to the forum! There are a lot of really knowledgeable people here.