Before being able to add the widget to your Google Sites powered website, you must first find your Provider ID. This can be done on the "Site Integration" page (https://goteamup.com/providers/widgets/). It is the number outlined in red in the screenshot below, 1234.
After you have your Provider ID, go to the page editor on Google Sites where you'd like the widget to appear. Under the "Insert" menu, select "More Gadgets".
On the window that appears, select "Add gadget by URL". Enter http://assets.goteamup.com/static/widgets/google_sites.xml as the URL. Then click "Add".
On the next screen, you can configure the widget. Enter your Provider ID and then select the default tab and set the width and height. Note: The Google Sites widget does not yet support the "Free Trial Widget" functionality.