You can create any email address that you would like right in the Site Manager under "Email" -> "Accounts". You can set your own passwords and quotas here, as well as get your settings to download email into a client such as Outlook or Mac Mail.
In order to download your mail you will have to configure an email client such as Microsoft Outlook or Mozilla Thunderbird.
The following are the settings you should use:
-------------------------------------
Secure SSL/TLS Settings
-------------------------------------
Username: user@yourdomain.com
Password: Use the email account’s password.
Incoming Server: yourdomain.com
IMAP Port: 993
POP3 Port: 995
Outgoing Server: yourdomain.com
SMTP Port: 465
Authentication is required for IMAP, POP3, and SMTP.
-------------------------------------
Webmail
-------------------------------------
You can view your mail online by going to:
http://yourdomain.com/webmail
Username: user@yourdomain.com
Password: Use the email account’s password.