To select a trigger in the Journey Builder, you need to create an automation in Mailchimp.
Creating an automation
In Mailchimp, go to the following link: https: //us14.admin.mailchimp.com/customer-journey/#/create-campaign/explore/emailCampaign:custom
Click on 'API' and then 'API 3.0'.
Give the campaign a name, select an audience (only profiles in the audience can fire the trigger) and click 'Start
Design the email by clicking on 'Design Email
Click on 'Confirm' and 'Start Sending
✅ The trigger is visible in the Journey Builder