If you used EventBrite for your ticketing, their system provides a way to send an email to all the ticket buyers for that event.

Just go to EventBrite and log in to your account (note that the login/password probably isn’t the same as for GoSeeDo - it’s whatever you used when you created your EventBrite account yourself).

Find your event in your dashboard, then, once in the event, click the “Email Attendees” link in the left column.

Back on GoSeeDo, open your event page and look for the link "Thank Buyers" inside the "Promote this Offering" section in the side bar. Clicking on that link will bring up the template in a new window.

You can select all in that window, and then copy and paste the text into the EventBrite email editor form. Make any edits you want, and click send.