accessing pre-installed libraries

I am trying to access a pre installed library (the WiFi library more specifically) the way you can access any library you installed, in order to properly view the functions and possibly change some of the hradware defintions, is there a way to do this?

nogeden:
I am trying to access a pre installed library (the WiFi library more specifically) the way you can access any library you installed, in order to properly view the functions and possibly change some of the hradware defintions, is there a way to do this?

Yes - navigate to the folder containing the library, open the source files and read them. (Then modify as necessary, if you know what you're doing.)

If you say what OS you are using and what version of the IDE you are using someone could supply specific directions.

For example on Mac OS X 10.11.1 and Arduino IDE 1.6.6:
Go to the Applications folder, Control-click on the Arduino app, and select "Show Package Contents" from the drop-down menu. You will find the sources in: Contents->Java->libraries->WiFi