reCaptcha on contact form

reCaptcha works fine on my login screen. I would like to add it to my web contact form as well. Have checked every possible box in the settings, but it doesn’t work/appear on the form…Do I need to add anything to my code as well – like Google explains on their reCaptcha setup page? Or should wp-cerber do the job automatically? The form is a simple hand-coded version on my contact page…Thanks in advance for your help / advise. Kind regards