Add example of how to configure location of a journal

[matthiasbeyer]

Closes #2019

I have read this two or three times before opening #2019 but it definitively didn't click.

So here I add an example, which makes things clear.

I am not sure about the markup being correct though. Feel free to guide me to correct markup 👍

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.