There is no direct way to add this. You can follow https://www.shamimsplugins.com/docs/advanced-nocaptcha-recaptcha/getting-started-advanced-nocaptcha-recaptcha/implement-in-custom-form/
Or you can use any supported contact form (eg. Contact Form 7) to create your form. To implement in Contact Form 7 follow https://www.shamimsplugins.com/docs/advanced-nocaptcha-recaptcha/getting-started-advanced-nocaptcha-recaptcha/implement-in-contact-form-7/