Since you already have your betta, I guess it's too late to do a fishless nitrogen cycle.
But these threads will help you through the cycle.
The plants you buy should be silk since they don't tear a betta's delicate fins, and the real plants are great for a betta :)
Since you have real plants, please make sure they have adequate lighting for growth, or else they will rot in your tank
and that's bad for your betta :(
Make sure the tank is at least heated, and better yet filtered.
Please post pics of your betta!