It’s very easy to add Common Ninja’s HTML code to Google Sites.
1. First, you need to copy the widget’s HTML code. There are several methods to do so.
Method 1: From the Widget’s Editor
Once you’ve saved your widget, at the top right corner, to the left of the “preview” button, you will see the “Add to Website” button, represented by the “</>” symbol. Click on it.
Then, in the window that opens up, you will see the code. Simply click on the copy button next to it.
Method 2: From the Dashboard
From your user dashboard, find the widget you want to add to your website from within the “Widgets” tab. Next to it, and under the “Actions” heading (on the right side), you will see a purple button with “Add to Site” on it. Click on it.
A window will pop up, and here, simply click on the copy button next to the code to copy it.
2. Next, open your google site and click on “Insert”. Then, click on “Embed”. Choose the option to “Embed code” and paste the code you’ve copied before into the field. Click “Save”. That’s it. You should see Common Ninja’s app on your page.
Source: Google