In order to active, the Hero Message with Button Links setting, navigate to Settings >> Design Settings >> Homepage >> Top Hero Section >> Search Module / Call to Action  >  Click on Search Box / Call to Action. Select the Hero Message with Button Links option:

This will activate the following fields:

- Button Text: Add the text to be displayed. Example: Join Now

- Button URL: Add the permalink that the button will link to. Example /join

- Button Class: Choose the type of button. To learn more, click on the following article Default Button Link Colors

This is what a homepage looks like when using three buttons: