WordPress Plugin
Connecting the API Key
First thing you need to do is navigate to your WordPress->Settings->Buy Now Plus
That will take you here,
How to add button into a page or post
Adding a button to WordPress page couldn’t be easier, however with the new Gutenberg editor I will need to show you the differences in adding a button vs Classic editor.
To add a Buy Now button to a page or post make sure you have already Installed the But Now add-on and linked the API as shown Here(Install) and Here(API).