On the Common Ninja website, after you've created your RSS Feed, copy the widget code.
Go to your Common Ninja dashboard, look for the RSS Feed you want to install, click the "Add to Website" button, and copy the widget ID:
In your Wix My Sites admin panel (wix.com/account/sites), click the Site you want to edit. Once in the site dashboard, click the plus icon, More, and click Embed a Site.
Click Enter Website Address:
In a new pop-up, select Code under the What do you want to add? Section and paste the code. You will see your plugin updated in the field. Since Wix is a drag-and-drop editor, you can simply resize and arrange it any way you want.