You pin it down to the dimensions you want and use the steam from your iron. Or if you have one of those house-cleaning steamers, I've seen people use those, too.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry