Choose Insert, then More Gadgets.
In the Google Sites Editor, open the Insert menu. You will be able to see a list of gadgets you can add to your site, like Links, Tables, and Images. Click on the More Gadgets option. This allows you to install customizable tools such as the POWr YouTube Gallery to your site.
Paste in URL
You will see the Gadget manager. Click 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 YouTube Gallery Widget onto your website, you'll probably want to change the shape and size of the Widget. Use the different options in the window to select the height and width of your plugin. If you'd like, you can add a border, title or scrollbar to your YouTube Gallery Widget, but we don't advise it. You will have more editing options through the plugin.
Set up POWr YouTube Gallery
Go to your live Google Sites website and select the Settings Icon in the upper right corner of the YouTube Gallery Widget.
In the POWr Editor, click Import Existing YouTube Gallery, find YouTube Gallery- and click Copy.