The dealer form is rendered by us, inside your page, so it does not inherit your theme styles automatically. There are two ways to bring it in line with the rest of your site.
The per-field settings
Go to Settings → Dealer form, find the Form fields card. You can reorder fields, add or remove them, and mark them as required. For colours, alignment and other styling, use custom CSS below.
Custom CSS
For anything beyond that, the Custom CSS code card on the same page takes your own stylesheet: fonts, spacing, button shapes, borders. Paste your rules in and save.
Two things worth knowing before you write any. Check the result on a phone as well as a desktop, because the form is narrow on mobile and generous padding stops fitting. And keep enough contrast between text and background: a form nobody can read is worse than one that does not match.
Not a CSS person?
Tell us in the chat what you want it to look like, or send a screenshot of your own forms, and we will write the CSS for you. It is a small job for us and it saves you an afternoon.
What to do next
Changing which fields appear at all, rather than how they look, is "How to manage form fields in the dealer form".
The wording inside the form is translated separately, under Settings then Translations.
Stuck on any of this? Open the chat in the bottom right corner of the app and we will help you set it up.