how to add my email signature for the email automations?

Check out this thread: https://community.airtable.com/t5/automations/add-signature-to-the-gmail-send-email-automation/td-p/66421

The recommended solutions are to either use a third party automation service such as Zapier or Make to send out emails with a signature, or to format the signature yourself with HTML and apply it to your Airtable automation action

I tried to use html and it didn't work for me

You can add your work email signature to email automation by including it in your email template. If you're using an email marketing platform (e.g., Mailchimp, HubSpot), edit the template and insert your signature as an image or HTML block. If you're using Gmail or Outlook, set up a default signature in settings and ensure it's applied to automated emails. Let me know which platform you're using for more specific steps!