You can run an advertisement that will appear adjacent to any story you publish in your Newstitan.org account.
You'll need to create the advertisement in advance, as an image (i.e. jpg, gif) and then link it to your story post in Newstitan.
728 px wide
Height can be anything you'd like.
Inside your post look for the "Custom Ad" section. This is where you will insert the image and the URL it should like to. It looks like this:
Make sure you save your post so the ad gets saved and inserted.