First off welcome to the forum. I wouldn't worry about doing anything wrong here, when you consider some of the stuff that shows up! Ha ha!
To answer your question:
I haven't tried recording a video of me playing yet, but I would imagine an actual video camera instead of your cell phone and some audio recording software with an interface (usually comes with the recording software), and a microphone, would be a good place to start. I'm not saying this to be an A-Hole, just that's what I would look at if I wanted to tackle your project.
For around $150 you can get a 2 channel interface with recording software and just use a direct out from your amp, or simply plug your bass into the interface and you're good to go.
Anyway, I hope this helps to answer your question.
Carvin Club #167
Switch-Hitter #25 (musical switch-hitter you pervs! Musical!)