I just bought a betta fish today... Have no idea how to take care of one...

I have a round fish bowl.. My friend said to put bottled water in it, not distilled. My question is: is there a difference between purified water and distilled, or are they the same? Cause I have Aquafina bottled waters...

Second question.. I'm told if I put a plant in it, It means they can stay in there for months without me changing water... I have a bamboo plant, already in it's vase.. Do I just plop it in there with the water it has, or do I have to wash it and put it in new water? (that sounds like a stupid question, but I really have no clue)

and If I have to change the water how often should I change it?

Is about food: I bought some pellets for it, the lady said feed them one pellet once a day... That seems like so little, is she correct?

also I was told depending on what you feed them they can change colors?

Sorry for asking so many questions... I just want to make sure I dont end up killing him.

-Ferdinand