To add a form to your Google Sites page, select the Publish button from the top right corner of your Form Editor. From the options available on the left panel, select Embed.
Access your Google Sites page and select Insert to add a new element to your website. From the available options choose Embed.
A preview of the form is displayed. Finally, press Insert in your main view.
Place the form in the section you need on your webpage and drag the blue margins to adjust its height and width.
Finally, press Publish to save the changes to your website. You can now share your web page with others and collect the leads or contacts you need.
Important NoteIf you are using the old version from Google Sites, use the iframe code of your form (Embed Code → Iframe).