Within EPIC software menus, you should be able to see and modify the configuration fuses.

If you want to edit them, well do it within EPIC software then save changes (make sure you made abackup of the file BEFORE)

If you want to use another Crystal/OSC value, you'll also need to modify the Bootloader firmware, it use USART so you want to spot the related USART registers (SPBRG, RCSTA at least) to alway keep the same Baudrate.

Scalerobotics did a short tutorial in the Wiki that show 1 method to deal with it.

PS: broken record again...