Welcome to the Airtable community!
Airtable’s native forms have almost no styling options. You can change the text of the submit button on the bottom and add some pictures to the top. That’s about it. If you want additional styling, you need to use a 3rd party form integration. Some form services, such as JotForm integrate directly with Airtable. Other 3rd party form services will also require using Integromat or Zapier to integrate the form with Airtable.