If you want to use CFW outside of your home/wifi access you have to downgrade to 4.x, this is so you can use the DS Profile Exploit which doesn't require internet conection.
The first thing you HAVE to do, is backup your system nand using gateway's launcher.dat, so if antlything goes wrong your 3DS won't be permanently bricked, downgrading the 3DS is pretty safe but you can never be too causios, BigBlueMenu is an app that allows you to install cia games into your SD memory card, you *don't have* to install it, you can just use FBI to install your games but I rather use BBM, it has a nice and easy UI and allows you to delete games that you no longer want to play.
If I was you:
1)Use gateway's launcher.dat to backup nand and copy it to your PC.
2)Use gateway's launcher.dat to format emunand.
3)Copy rxTools files and update emunand to 9.9
4)Use fbi injection and install BigBlueMenu.cia
5)Get some cias and install them.
6)???
7)Profit