If you are using Outlook Express, you may find the following step by step instructions of use.
Open Outlook Express
Click 'Tools' (on the toolbar), then 'Accounts' (from the subsequent drop down menu)
Click the 'Mail' tab at the top of the resulting 'Internet Accounts' window
Click 'Add' > 'Mail'
Enter your name in the box provided, in the form that you would like the recipients of your mails to see, and then click 'Next'
Check the radio button to say that you already have an email address, then enter your email address firstname.lastname@example.org and click 'Next'
Select 'My incoming mail server is a POP3 server' (should already be selected by default)
Enter the Incoming Mail Server as shown in the table above in the 'Incoming mail server' box
Enter the Outgoing Mail Server as shown in the table above in the 'Outgoing mail server (SMTP)' box
Enter your email address email@example.com in the 'Account name' box
Enter your password
Ensure that the 'Remember password' box is ticked
Double click the resulting email account, and go to the Servers tab. At the bottom of the form (Outgoing Mail Server), tick the box which says 'My Server Requires Authentication', and then click 'OK'.