Navigate to Settings >> Design Settings >> Homepage >> Top Hero Section >> Search Box / Call to Action  >  Click on Select Call to Action. 

Select the Display 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.

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