After creating your event in Boomset go to the "Import a Guest List" tab and select "Start Import" next to Connect with Aventri (Formerly known as Etouches).
As long as you are the main Etouches account holder and have linked your Aventri (Etouches) account in your Boomset profile your events should start to populate.
Choose which event's guest list and settings you would like to import by selecting Import towards the left of the event name.