Just drag and drop the block inside all the screens or just drop it inside a block which is present in all the screens such as menu block.

That's it!

Publish the module. Rest of the things will be automatically taken care. Your application will prevent the concurrent logins made by the same user.

For Multiple Frontend Server Environment Setup

-Replace BroadcastChatMessage service action with BroadcastToAllServer service action. (BroadcastToAllServer Service Action based on SSE Push Event Hub Multiple Frontends POC)

Publish the single signin user component in your environment.

1. Open the manage dependency and the selected elements in the below image,

2. Drag and drop the UserLogin client action right below the login action,

3. Drag and drop the SingleUserSignIn block in menu block or in any block which is present in all the screens or directly drop the SingleUserSignIn block in all the screens.

(In this documentation, block is added in the menu block)

That's it! 

publish your module and see the result by login to the application with same user id from two different browser or devices as shown in the below image.