Hello @DwightO9 ,
Are you trying to add an embeddable form (inline or pop-up) to your email? Emails can't have forms embedded into them, so if you're wanting to share a sign up form via email you can insert a landing page sign up form's share URL.
Click here if you need additional guidance making a landing page sign up form.
If you're needing more than one list as an option, you can use the legacy Basic Landing Pages found in the Sign Up Form tab.