Issues while accessing system files with su in Chinese make Tablet. (Android 4.0.3) I have a cheap chinese tablet with Android 4.0.3.

I'm a linux enthusiast and of course I wanna explore the Android capabilities deeper.(I own Nokia N900 and without rooting its nothing).

So my tablet is WM8850.

The interesting is that I can browse in the /, but when I ask for root 
privileges  su , it says that:

I'm not allowed to access prompt with su priviledges.

UID XXXX not allowed to  su.

So do I need to do the all rooting process or I just have to install the super user package?
You will need to get root privilege. Merely installing Super User won't do anything.
EDIT: 
SuperUser must be placed in /system (made a "system app") in order to work, which is not done by "merely installing it", and cannot be done without aquiring root privileges