How to stop edges from curling?

[reallydolly]

Hello! I am working on a scarf for my son for christmas. I'm a new knitter and I have finished a few other basic projects (scarf, scarf, and scarf). This is the first time I've done any kind of pattern - I've just been knitting stockinette.

I'm using alpaca on #11 needles. The pattern is 15 stitches across, K/P rows 1 -6, K 7-10, then repeat.