You can either: log on to Southwest, put in your info, and "check in" -- which will show you the boarding lass that EBCI got for you, and print it.
OR
When you go to the airport, go to Southwest, check in, and reprint boarding pass.
We are always checking bags -- so we go to Southwest line, use computer check in terminal, press check bags and reprint boarding pass.
If you are not checking bags: most airports have a Southest express kiosk where you can reprint boarding pass with little or no line (but can't check bags).