Trim the umbilical cord with dull scissors or shred the cord between your fingers. There will be less bleeding from the cord if you crush the cord as you are tearing or cutting. If there is any bleeding from the stump, tie the cord off near the end with dental floss. After the cord is trimmed and tied, dip it in iodine. This helps dry it out and also helps to keep infections from entering through the open blood vessels. A neatly trimmed cord, coated in iodine will keep your bitch from excessively worrying the puppy's cord.
http://www.phi-vestavia.com/whelpingmanagement.htm
It you want to shred, you clamp then you crush the cord and use your finger nails to shred.
or here is for clamping and tie
http://www.debbiejensen.com/umbilic_cord.html