1. You have to create a user with uid 202: dovecot
2. And a group with gid 202: dovecot
3. Configure dovecot config file: /etc/dovecot/dovecot.conf
   There is already an example file included in /etc/dovecot/

NOTE: Step 1-2 can easily be done by 'sh config-helper.sh' in current
directory.

Have fun :-)