You can add a form to appear as a pop-up on any button on the page you want. To do so, follow these steps:
Go to the edit section of the form you embedded to the storefront in the previous step.
Go to Form Settings -> Form load as popup -> Check the Enabled form as a pop box -> Check the Form load as popup with existing button checkbox
Go to the storefront, hover over the button where you want the form to appear. Right-click and select Inspect. From the highlighted div class, copy only the text within the quotation marks up to the first space.
Paste it in the Form load as a pop-up with an existing button class/ID field
Watch the video for detailed instructions: