How do I add a 'accepts marketing' tickbox in a typeform so I can include or exclude people from the Klaviyo integration?

Hiya, I have the Typeform and Klaviyo integration setup so that when someone submits a form, they automatically go through to klaviyo and into a flow that sends a ‘thank you for your enquiry’ email. Ideally I would like to add a tickbox in here to accept or not accept marketing so that we could then add them to our welcome series if they are not already on our database but obviously from a GDPR perspective we need to ensure people are physically opting into this.