Recommended article before setting up: Engage: Page Targeting
Similar to the Email Alert Bar, this CTA is designed to sit at the bottom or top of your site and allow visitors to click to a page destination for a call to action you want to make available on your site. When a longer form is needed and an Email Alert Bar just wont do the job, use the CTA alert bar!
To use this call to action:
Set the appropriate text, font size, and colors, and button link
Choose an appearance, condition and position (see: Editing Your CTAs)
Choose a Lead Form (see: Understanding your Lead Forms )