When you need to update an email template, you do this at the blueprint level. The changes will then sync out to all associated accounts.
Step 1: Find the template
In the left-hand navigation, go to Communications and select Email Templates. You'll see a list of all your existing email templates, along with their category, language, and when they were last updated.
You can use the Search templates by name field to find a specific template, or sort the list by clicking any column header.
Step 2: Open the template for editing
In the Actions column for the template you want to update, click Edit.
Step 3: Make your changes
Update any of the fields you need to - template name, category, email body, subject line (if using an advanced template), or any language versions. As you type, the template preview will update to show how the email will look to customers. Save the blueprint when you're done.
Step 4: Save and deploy your changes
Saving doesn't push the changes to your accounts on its own, but it will take you back on the summary page. The blueprint will show a status of Pending Update so click Sync All to deploy your changes across all associated accounts.