Hey! Welcome to the forum! Make sure you read some of the "pinned" or "sticky" posts that are at the top of all the forums; they have some good information about some of the common questions people ask.
Good luck with your betta! Have a look at some of the articles or posts about cycling a tank. You'll need to keep up with the water changes for your betta and if you feel like spending some money later on you could consider getting a larger tank with a filter and heater which your betta would appreciate because you would then be able to maintain a more stable environment.
Anyway, have fun reading. I've learned lots since I joined.