[Dovecot] new mail server

[Allen Sim]

Hi i am a newbie in setting up a mail server.I am using CentOS and
complete installed OpenLDAP,pam,dovecot,sendmail & squirrelmail.
Now, how should i start to send & receive through the mail server?
How should i add a user and try to send & receive mail?
I am trying to use Thunderbird...but how should i start?
Please advice... thanks