If you are on the latest version of the app, we will do this by default.
Some highly customized themes may not work out of the box. If you are on the latest version, but not seeing the buttons on out of stock or unavailable to purchase items, let us know, and we'll be glad to help you make the proper edits for the buttons to show.
Checking what version you are on:
Note: Only Store Owner or Admin users can see these menu items.
The latest version (V4)
You will see a "Form and Buttons" link in your dashboard
Previous Version (V1-V3)
You will see a link to "Install Code"
If you have extensive B2B Ninja customizations, it's likely you are on this version.