To set up an automated welcome email, you will want to first make sure that you have set up your Mailchimp integration: https://help.trypico.com/en/articles/2906271-integrating-mailchimp
Additionally, we recommend updating your Mailchimp footer so that users update their preferences within Pico and sync back to Mailchimp properly: https://help.trypico.com/en/articles/2906094-essential-changes-to-your-mailchimp-templates-when-using-pico
Once you have done this, you'll be ready to set up some automation. Within Mailchimp, you will want to navigate to the automations tab, then select "Emails"
Once selected you will see a new prompt asking you which type of email you would like to create. Select the "Welcome new subscribers" email.
Next, give your email a descriptive name so that you can reference it later. Then make sure that the audience selected is the one that Pico is syncing information to and select "Begin".
Mailchimp will then redirect you to a page where you can modify the newly created campaign. You can adjust the time that it sends the email to be a few hours afterwards or immediately. You can also make changes to the subject line. Then you can work on building out the content of the email.
Once you have completed the steps to build out your email, you can then select "start sending" to activate the campaign and have welcome emails be sent after someone registers on Pico!
For tips on how to best design the content of your email, we recommend reviewing Mailchimp's email design guide here: https://mailchimp.com/email-design-guide/
For some welcome email best practices we recommend our guide on welcome emails here: https://trypico.com/thebyline/email-marketing/welcome-email-guide