To manually add news content, go to Add Content -> Photos -> Manual. This will automatically create new collection which you can additionally modify to your needs.
To add item to that collection, click on "+add item" and fill in the content.
That way you can add as many collections and items as you want.
You can add feed from Instagram by selecting Add Content -> Photos -> Instagram. Simply enter username or your Instagram link and import.
You can add Flickr feeds by typing in Flickr username or direct link to Flickr photo feed.
To add RSS go to Add Content -> Photos -> RSS and paste the RSS feed link.
Here are your added photos:
Once your galleries are configured, placing them into your app will result in a similar interface to the one below :