A Lightbox is a technique that opens a form in front of your content when you want it to show. Here's how.
1. Go to Marketing Activities.
2. Find and select your form.
3. Under Form Actions, click Embed Code.
The form must be approved for the embed code item to be visible/useable.
4. Set Code Type to Lightbox.
5. Select/copy the code and click Close.
Hand the code over to your web developer and have them add it to your website.