Note that guide is for vintage themes, newer themes like OS2.0 need the code and steps adapted using knowledge of html & liquid.
And this is vastly different from the “messages” being actual separate purchasable products like a physical greeting-card.
If you need this customization you can click here to mail me , or contact me by mail for services using the contact info in my forum signature.
ALWAYS please provide context, examples: store url, theme name, post url(s) , or any further detail in ALL correspondence.