Requests can be made to other users to write an article. This will send the request and assign it to them, and then notify you when the article is approved and published.

The best way to do this is by creating the draft yourself. You can then add hidden comments in the draft, and click on "Reassign Draft" to select who should complete the article. They will then receive an email with the link to the article, and will see your comments/instructions and when they are done, publish the article. Remember to select "Return to Me Afterwards" to ensure that when they publish you get to see their work so it can be reviewed before publishing.