How can I link multiple gmail accounts?

When I tried to link a few accounts, it asked me if i wanted to use pop or smtp, I tried both but neither works.
How can I link multiple gmail accounts?
With Gmail it is really easy, just go to settings up in the upper right hand corner-ish, and then go to the Accounts tab. There will be a section that says get mail from other accounts. Add one to the other, then above that there will be send mail as, and configure that too and you should be set.
Reply:you need to decide on 1 as your master account, then set up for that account to retrieve your other accounts emails by POP. You will need to input all of the necessary POP settings as well as enable it in your account settings.
Reply:you have to use pop and the pop address is pop.gmail.com