If you are using avrdude, and a USBtiny programmer to program your chip, then this is how you set the fuse bits.

avrdude -c usbtiny -p t85 -U lfuse:w:0xc1:m -U hfuse:w:0xDF:m -U efuse:w:0xFF:m

http://www.ladyada.net/make/usbtinyisp/

http://www.ladyada.net/learn/avr/avrdude.html