In the Settings Section of the Admin panel, go to the Site Settings section.
Here you need to specify the Email Server Address. If you do not know what email server address to use, you will need to contact the host and ask them about sending emails using a php script.
Also, on the Store Emails and Registration Emails tabs, you will need to Specify the subject and the From Address for the emails.
On the Contact Form Emails tab, you will need to specify the To Address for where the emails should be sent to.
The To address on the contact Form emails tab and the from address on the registration and store emails needs to be a valid email address for your domain.