Brenda's right--you can only use circs in the 'normal' way for something that is at least as big around as the circs are. Then you have to go to dpns or another circ technique.
There are mitten patterns that are knit flat, with a seam, if you don't want to tackle dpns. I say to give the dpns a shot, though. They're really not that difficult and it's an excellent skill to have.