[Dovecot] How do I get my mail from fetchmail into dovecot?

I have dovecot (with squirrel mail etc.) running without any problems but cannot understand how to get e-mail from a pop server into dovecot. I have fetchmail configured to pick up the mail from the pop3 server but don't understand how to get it from there into my dovecot mbox structure.

New to mail servers!

Thanks,

Michael.