I signed up for early-bird boarding with Southwest for the first time. How will I access my boarding passes? Do I have to login to my account and check-in? Will there be any notification from SW when I login to my account that the passes are ready to print?

You can print your boarding passes at airport if you want or at home. You do not have to check in, per se; that is what Early Bird is for. The boarding # will be assigned 36 hours before flight. Boarding Passes can be printed beginning 24 hours prior to the flight's scheduled local departure time. Log into the website as if you were going to check in with conf # and name. It will then take you to where you can see your # and option to print.

if you are checking luggage there is no advantage to pre printing passes, as you will have to go to the kiosk anyway, and you can print them there.