You can send the content from a persona. To see the Personas' menu, you need to click "Personas" at the top bar.
To change the persona who sends a content, click the persona's name that appears in the card. Select one of the personas from your list.
If you reset the first login, upload the scenario and then log in, you should see the same as the screen shot below.
Notice that now the message comes from the persona, Carl. It looks more interesting already.