Choose Insert, then More Gadgets.
In the Google Sites Editor, find the Insert menu, and open it. You should see a list of available components and gadgets you can add to your site, like Images, Links, and Tables. Click on the More Gadgets option. This lets you add editable tools such as the POWr Multi Slider to your page.
Copy and Paste
The Gadget manager will appear. Choose Add Gadget by URL. Copy and paste this URL into the box. Select Add to finish.
Adjust Height and Width
Now that you’ve added your new, customizable Multi Slider Widget to your Google Sites page, you’ll probably want to adjust the size and shape of the Widget. Use the options in the pop-up to choose a height and width for your plugin. If you'd like, you can add a border, title or scrollbar to your Multi Slider Widget, but we don't advise it. You'll have more control while editing right through the plugin itself.
Set up POWr Multi Slider
Go to your live Google Sites website and click the gear icon in the upper right corner of the Multi Slider Widget.
In the POWr Editor, click Import Existing Multi Slider, find Multi Slider- and click Copy.