Ticketless means no paper sent to you in the mail. Your email lists your confirmation number (you will need that).
If you did not do Early Bird check-in, here's the deal: at 24 hours before your flight (to the minute if you can manage it, you can't do it earlier) you should be logged into the SW website, have your confirmation number typed in and ready to check-in the people in your party. You then get an electronic boarding pass with a boarding letter (A, B or C) with a line number of 1-60. You can print that boarding pass, or reprint it at the airport when you check in bags. (If you have no bags to check, you can walk up to security with your printed boarding pass and ID, and proceed to the flight gate (which you would learn from the electronnic displays at the aiport).
At the gate, SW usually starts boarding at least 30 minutes before your flight (if the plane is there) and will you stand in line when it corresponds to your Letter (and in orfer by number). The plane boards in the following order: people needing assistance, A group, people with small kids, B group, thern last C group. You choose any open seat(s).