@Jeliwickle
I
literally wrote the guide on this, so believe me when I say that if you're a 13 year old with no soldering experience, I can practically guarantee that you're going to ruin your DSi. Go talk to someone at your local cell phone repair shop, they'd likely be willing to help you out. Or, if you're lucky enough to have a friend or family member that's at least an electronics technician, take it to them. The points you need to solder on your console are no place to be starting your soldering practice.
If you absolutely must do it yourself, take apart some old VCRs or DVD players and get a nice 35W soldering iron with a pencil tip, some leaded solder, and some good soldering rosin flux. Plumping flux won't cut it, it's acidic and will eat away at your circuit board and passive components over time. Also get a pair of simple magnifying jeweler's glasses, they're important when you're a novice trying to work on SMD components. Oh, and safety glasses are important too.
Get as much practice as you can removing and reattaching components, and make sure you do it in a well ventilated room, as the flux fumes are harmful to your health in larger quantities.
Here's some videos I've archived on soldering that may help you get started.
http://www.mediafire.com/download/80gmyc0e6jl14vr/PACE_Soldering_Videos.zip
Password: gbatemp
Whichever you choose, I wish you the best of luck, and I hope those resources help if you choose to learn how to solder.