Choose Insert, then More Gadgets.
In the Google Sites Editor, open the Insert menu. 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 allows you to install customizable tools such as the POWr Photo Gallery to your site.
Paste in URL
You will see the Gadget manager. Choose Add Gadget by URL. Copy and paste this URL into the box. Choose Add to complete.
Change Height and Width
Now that you have embedded your new, fully customizable Photo Gallery Widget onto your website, you'll probably want to change the shape and size 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 Photo Gallery Widget, but we don't advise it. You will have more editing options through the plugin.
Set up POWr Photo Gallery
Go to your live Google Sites website and select the settings gear in the top right corner of your Photo Gallery Widget.
In the POWr Editor, click Import Existing Photo Gallery, find Photo Gallery- and click Copy.