Open Thunderbird.  If you are using Thunderbird for the first time this will initialize the email setup wizard.  Select "email account" under New Account Setup. Click Next.

Enter your name in the field provided.  This is the name that will appear in your email recipients inbox when you send them an email.  Most people enter their first and last name in this field. 

Enter your complete email address.  Click Next.

Ensure that POP is selected for incoming Mail server.

The incoming mail server name is pop.pacificonline.com.

The outgoing mail server name is smtp.pacificonline.com.  Click Next.

The User Name for both the incoming and outgoing profiles is your complete email address.  Click Next.

You can choose any account name to identify this account. Click Next.

At this time verify that all information is entered correctly. Click Finish. 

You should now be in the main menu.  Open the Tools menu, and select "Account Settings"

Select Outgoing Server (SMTP) and change the Outgoing Mail (SMTP) port from 25 to 587. Click Ok.

Your Mozilla Thunderbird program is now set up and ready for use with your Pacific Online email account.