You can follow along the steps in this doc to Edit an existing template. Changes made to a template won't alter your automations that use the template.
Step 1: Navigate to the templates page
To create a template navigate to the Templates page and click the Edit on the template you want to edit.
Step 2: Edit your template
In the email composer, edit your email template. Every element you add here will be available when you select the template in your newsletters and automations.
Step 4: Save and Exit
Once you're done creating your template, click the Save and Exit button at the top-right of the screen.
That's it you've edited a template with SmartrMail 🎉