- Go to: Magento admin panel >> System >> Transactional Emails >> Create New with MTEditor.
- Choose email template and locale from the list
- Enter template name and press the button "Create new"
Now you have to apply this template in system configuration. For example if you have created "Newsletter subscription success" email template you have to go to Magento admin panel >> System >> Configuration >> Newsletter >> Subscription options >> Success email template and choose your new template.