In WooCommerce, with every order, comes one or more emails. WooCommerce sends automatically to the shop manager or to the customer, depending on the current step of the purchase process and they have some pre-defined messages.
These messages change based on the email sent and there are no options to change them. Sometimes you may need to add more text to all emails, such as a notice that says that the order is an online order. How do you do this?
Guess what? Custom code!
Before implementing any code changes, always ensure your site is backed up. This will help you restore things in case of unforeseen errors. I recommend using Jetpack Backup for real-time backups and one-click restores.
Open the file functions.php in wp-content/themes/your-child-theme-name/ and add this code at the end of the file:
This will add the specified content right after the header section of the email but before any pre-defined content.