In the Emailify export panel, select the Resend option from the dropdown list, then paste in a valid Resend API key.
If you want Emailify to publish the template immediately after it is uploaded, enable the Publish Template toggle before exporting.
When you're ready, click the Upload To Resend button to start exporting the emails you've selected from Figma to HTML, and have them automatically be uploaded to your Resend templates.