Here are step by step directions to adding ads to your web view Social Hub Mosaic.
Please open your dashboard and select the gear icon in the desired Social Hub Moasic.
Once you've clicked the gear it will let you manage the Web View...
At the bottom center of the page ... click the "Customize Layout" link.
Then click the "ADVERTISEMENT" tab
Now that your managing the "ADVERTISEMENTS" you can "Choose File" to add into your system as a native ad.
Please use your best judgment when sizing your native ads.
As a rule of thumb don't use heavy large images.
Always use "save for web" option when possible.