In order to embed StoriesOnBoard in Confluence, first please log in to Confluence and select Apps › Find new apps.
Search for StoriesOnBoard and select it.
Click on Get app and continue by pressing the Get it now button.
You should get a notification in case of success.
After that you can go to the page you like to insert StoriesOnBoard and click Insert › View more, then search again for StoriesOnBoard and select it.
Open the story map you like to embed in StoriesOnBoard and visit the Share menu.
Switch to More sharing options, enable Private link sharing, and copy the link to the clipboard.
Now you can head back to Confluence, paste the link to the Url field, and click Insert.
After a few seconds, StoriesOnBoard should show up on your page. In order to edit your story map in Confluence, you need to Publish the page first.