How do I add custom CSS to a Hubspot form?

I would like to add my own custom CSS to a hubspot form. Is there an input box or something where I can add my own CSS styling to the form?

@SMarritz You have to add your custom form styles to a stylesheet, e.g. in your main/global css, or if you want it for a specific page, you could add styles in a <style> tag in the advanced options of the page.