To add custom HTML code, click New email/template --> Basic templates --> My HTML.
In the code editor, insert your code.
Important to note: When you insert your own code, the standard functions of the editor menu will not be available. They will have no classes that are required for this. As a result, you will only be able to replace images and edit the name of the buttons (if there are any in the email)
To adapt your code to the editor menu functions, you'll need to add our classes.
For more details on how to do this, refer to our blog post.