Hi,
The CONFIG parameters are used to set the desired OSCillator setting you need, Internal or External.
You can also select Pin RA6 to output Fosc/4
If using the Internal Osc you also need to set its frequency in your program code using the OSCCON and other registers.
The 4550 can seem quiet confusing to set up with its PLL and USB options.
The 4550 datasheet contains all the options / parameters.
If you want more detailed help then say what frequency you want to use and what programming language you use.