PrestaShop 1.6.x. How to edit order confirmation and registration emails

Translation tool in the backend

1. In your PrestaShop admin panel go to Localization -> Translations section: 
2.  Find there Modify translations section. Select the E-mail template translations for Type of translation option. Choose Core (no theme selected) for Select the theme option. And select the required language. Click the Modify button: 
3. Open Core E-mail: and find order_conf: 
4.  You can change the body of the message after clicking on Edit HTML version. And also you can view/edit the .txt version: 
5. You can edit the account email in the same way: 
6. Click the Save button to confirm the action.

Editing E-Mail templates files that are located in your store

1. Go to your website Hosting Cpanel or FTP manager. There find Mails -> Your language folder.
2. You will see two files for combination E-Mails: .html, .txt. Download them and edit with any code editor (for instance, Notepad++ or Sublime2): 
3. Save the files and upload them to the same directory.

Hopefully, this tutorial was helpful for you.