well, i've been seeing some stuf of data visualization and i would like to try out some stuff with data, but.... how can i have data? is there a way to capture something into data that can be usable with processing? can it be stupid data like how frequently i go to the bathroom and stuff, wich i would write for a definite amount of time? is there data on the internet that we can use? sorry for these questions but i really wanna know

just use your imagination: processing handles numbers, text, images etc... (ok it's all numbers but you get the idea) just look around and choose your source.

it could be the csv file storing statistic data, the facebook profile pic of your friends or, maybe with a little help from an arduino board, how often you go to the bathroom.
reading the reference and playing with processing functions can give you a million ideas about how to collect data and, as phattee said, there are also a few books that could help you to think in the right direction.

code is no different than other expressive media: a painter has a few brushes, colors and canvas, but he has to look around in the world to decide what to paint. same thing here: processing gives you functions, types, the possibility to export in different formats, leaving you free to watch the world and handle a few samples from it