To add an emoji to a site message:
    Open the automation containing your site message.
    Locate the site message in your automation.
    Hover your mouse over the site message and click the “Edit” icon.

    Click the site message and click “Emoji.”
    Select the emoji you would like to insert by clicking it.
The emoji code is now inserted into your site message:

Click out of the box, and your emoji will display: