Create a signup form?

Create a signup form?

How do you create a sign-up form in Zoho Campaign?? I see that there is a basic sign-up form with just first and last name, and email address. 

On this page it says you can customize and add additional fields to the sign-up form:


"You can customize these forms to have additional custom or pre-defined fields to collect accurate information from your subscribers" 

And I see in several places where I can customize the look of the sign-up form (color, font, etc) but I don't see ANYWHERE how to actually create the sign-up form and add fields to it.

How do I do this??