[TYPO3] Edit Extension File

[rocky]

Hey List,
	
I'm using fdfx_2cols Extention, but I do not want use its CSS. I'm 
trying to change ext_typoscript_setup.txt in 
typo3/typo3conf/ext/fdfx_2cols.I got a message saying I do not have 
permision to do this.Anybody knows how to do that?


Thanks a lot in advance!
Rocky