Hehe welcome to the hobby! I'm kind of new too! Bettas are addicting! It started off as just wanting to have a pet to take care of, and getting a small fish tank because of the little room we have. And $200 later, we have an awesome fish tank. And just today my husband rescued a tiny betta girl from Wal Mart.
I have some things to recommend to you, because I found out the hard way by not listening to what people were telling me.
Plastic plants will most surely kill your betta's fins. I didn't listen. I wanted cool glowy plants to match my super mega awesome black light tank. A week after having set up that tank, Ninja Dude got a huge hole in his fin. I thought it healed back, but now he currently has fin rot which breaks my heart. Silk plants that don't have sticky edges, or live plants are ideal. Live plants put lots of good things in the water and absorbs a lot of waste that fish make.
A good heater is one that you can adjust the temperature manually, which is what I saw you had picked out on Amazon. Nice find. For a tank that small 25 watts will be more than efficient. Some brands that I recommend that you might want to look into are: Eheim Jagger, Hydor Theo (which is what I use), and Marineland just to name a few.
Also, a word about the tank. I know it's a four gallon which is more than plenty for Mr. Betta, but I should say, I think he'd be a lot more comfortable and have a better life in a tank like this: Clicky
It comes with a light, filter (which is better than the one in that tank you got), everything except gravel and food and decorations for only $30.
The tank I assume you bought your betta is this one? Tank
The bad thing about that tank, even though it's beautiful, and it will suffice in keeping Mr. Betta, is that it's as tall as it is wide. Bettas like to swim the most <----> This way, and not as much up and down. I also learned this the hard way. I used to think it was cooler to keep my fish in a tank that looked super awesome. But as I got to love my little guy more, I realized that I should think more about what's best for him. And in the end, the tank I got (which is the one I showed you.) ended up looking prettier and he's been happier since he's been put in it.
He used to glass surf in my other tank quite frequently. Glass surfing is where they rapidly swim back and forth or up and down along the glass in your tank, which means they're bored.
You don't have to take my advise. But it might be easier to return that tank now while you haven't used it, and save about $30.
Also, even though you didn't mention it in your first post, the right betta food is also important. Someone on this forum told me, which I find really helpful and true, is that you should never feed your betta something that has "Fish Meal" as it's first ingredient. Bettas can be really picky with what they eat. I've found that Omega One Betta Buffet Pellets
(they're currently out of stock but they usually restock fast and have very fast and inexpensive shipping) are what my betta loves the most. And unlike all other betta foods I've used and had to smell, this one actually smells like a seafood buffet. Like feeding your betta lobster! Betta foods I've picked up from pet stores and the like usually smell a little like rotting fish. Uck!
It's also good to feed your betta some variety. I use freeze dried blood worms and soak them first to get the air out. But a lot of people use frozen blood worms as well. I don't because I'm paranoid about bacteria. But most people seem to have no problem with it.
I hope this helps you! Good luck with your betta! Show us some pictures once he gets settled!