Get the data sheet for the particular chip you're using. There's a section on which bits of which fuse bytes need to be set to configure features such as this. I can't stress enough using the data sheet as the ultimate reference. Be very careful following guides. Take the gist of the instructions, but never copy the fuse settings from an example, as it may not do what you think it does.
The method by which to actually set the fuses is just a simple command line from avrdude. Here's a guide I found once while researching it:http://electrons.psychogenic.com/modules/arms/art/14/AVRFusesHOWTOGuide.php
I haven't tried it, but it looks about right from what I've seen.