Better customization options for Signup page

We would like to have more control over the Sign Up Link page styling (especially font sizes) so that it matches the style of our website. Currently the signup custom page looks very unprofessional. Our website is sugarcravingsfree.com which is the custom domain for our Heartbeat community. The page on our website that has the link to the Sign Up Link page is https://sugarcravingsfree.com/program/

Thank you