First, give the form a name. This is only used internally, so just give it a name that will help you and the other campaign managers on the account differentiate this form from all of the others in a list of forms.
Next, add some further information about this particular form. This information isn’t required but can be helpful in the future for figuring out which forms do what. This is also only used internally.
Click the "Next: Design my Form" button in the lower right hand corner to continue.