Give me steps to set up a pop3 email on mac 10.5 leopard

I still have 10.4, but it can't be that different in 10.5. I'm assuming you're using Mail, not Thunderbird or some other client? Have you looked at the help built into Mail? It's pretty clear, I think.

In 10.4, you add an account and on the Account Information tab, enter your email address. Get the incoming POP3 server from your ISP and enter it; it will look something like pop.something.com. Put the username & password from your ISP into the appropriate places. That should cover setting up the POP3 side.

In Mail, go to preferences, click accounts. Hit the "+" at the bottom left of the window. Fill out the name email address and password. Check "automatically set up account" and that's it. If it's a reasonably well known email service, it will do the rest for you.