Open Mozilla Thunderbird and go to File -> New -> Account.

Select Email account and click Next.

Type your name as you want it to appear on outgoing emails.
Then, type your email address in the field labeled Email Address.
Click Next to continue.

Select the radio button labeled POP.
Enter mail.ideaone.net in the field labeled Incoming Server.
Enter smtp.ideaone.net in the field labeled Outgoing Server.
Click Next to continue.

Note:  The field Outgoing Server is only visible during the setup of Mozilla Thunderbird's first email account. If you already have an email account set up, you will not see this field.

The next screen, User Names, should already be filled out correctly. Confirm that both fields match your Ideaone.net username, and then click Next to continue.

Note: If you have already set up an email account, the Outgoing Server field will not appear.

Click Next on the Account Name page to accept the default Account Name.
Click Finish.

The Account Wizard will display a summary of your configuration for your review. 
At this point you can check your configuration and go Back if you need to fix anything.

Immediately after clicking finish, you will be prompted for your password.
The default password is your account number and either nd or mn for the state your are in. 
A password example would be something like this: 999999nd  
If you'd like to save your password, make sure Use Password Manager to remember this password is checked before click OK to continue.

Note: You may see a dialog box describing how the Password Manager works. Click OK to continue.

Thunderbird is now setup to check your Ideaone.net account. Click OK to return to your inbox.