Generally Monday and Thursday afternoons from 1pm to 5pm (1pm to 4pm when not in Daylight Savings Time) and Saturdays from 10am to 1pm. Tides may affect lesson times, but correct info will be posted on the Announcements List. Detailed information on Dinghy Sailing Lessons is here.
You do not sign up for this lesson, just show up at lesson times. This lessons need lesson assistants, and you can signup for a lesson assistant role here here (you must be logged in).