Dropping a user removes that user from the database. You cannot drop a user who owns objects. Since there is no command to transfer ownership of objects, you must drop the objects before you can drop the username. To deny access to a user who owns objects, you can change his or her SQL Server password.
The databases of that server are listed.
The groups and users of that database are listed.
Or use the right mouse button to click on the username, and then from the drop-down menu that appears, choose Delete.
The username is removed from list, and the user can no longer access the database.