If you want your published story to be accessible via its URL but not appear in search engine results from Google, Bing or other search engines, you can exclude it from search engine indexing.
To do this, click on "Publish" in the editor sidebar:
In the publish dialog, activate the "Exclude from search engines" checkbox. This sets a meta tag that instructs search engine crawlers not to include the story in their index.
The story remains accessible to anyone who has the direct link. If you want to restrict access entirely, you can protect your story with a password instead.
If you want your story to appear in search results again, use the same workflow to publish it again – only this time make sure the "Exclude from search engines" option is no longer checked.
Note that it can take some time for search engines to pick up on the change. If you have Google Search Console set up, you can use it to inspect the indexing status of your story.