I assume you are connected to Shaw cable internet. If you are not using a router:
Open Mail, select Preferences, click on Accounts. Add a new account and configure it as a POP account. Your incoming mail server is shawmail and your outgoing mail server is shawmail.
Detailed configuration instructions for 10.3 Mail are
here. It's not much different for Leopard's Mail.
If you are using a router then you will need the actual domain name servers for incoming and outgoing mail for your city. Use
this page to enter your nearest city and find the required server addresses you will need to use.