Um, they hold the hen by the neck and climb on her back. It only takes about 15 seconds, his sperm goes in her oviduct to the ovum, fertilizes it as it passes through the ovum, then as it passes through her system the white forms and then the shell. I think the whole process takes a little over 24 hours, most of which is spent forming the shell. Does that help?
This made me think of somthing funny.
I had a little bantam rooster that would regularly "mount" our pet duck. The duck, who was much bigger than the rooster would run around the yard trying to shake him off.
I guess you could call it the Kenducky Derby. :