Add a shape to the new layer and size it big enough to hold the form
Right click the shape and select Web properties
On the Placeholder tab click the HTML code (body) button and paste the embed code in the dialog that opens.
If the embed code is in 2 parts - one for the header and the other for the body then use the HTML code (head) button insert to insert the header code.
Ok out of the Web properties dialog back to the web page.
Hide the popup layer
Create a link or button on the main web page layer so that when clicked the action makes the popup layer appear according the method you desire - Instant, slide in etc