For some operators, your e-ticket will be attached to the confirmation email with the 12Go voucher.
You must print it out and check in at the pier 2 - 4 hours before departure.
Others will only require the ticket number and give you a physical ticket at the pier.
And some partners will contact you before the departure to hand over the physical ticket before the trip.
Please check all the information in the trip description on the website and on the 12Go confirmation email and voucher before the trip.