To Run in Debug Mode
In the Package Explorer view, right-click your project.
Select Debug As > Mule Application.
Studio begins running the application in Debug mode, and displays a confirmation message asking you for permission to switch to the Debug Perspective.
Now your application is running in Debug Mode and the Debug Perspective loads additional views to track and manage breakpoints and expression watches.
Until an event arrives at the first breakpoint, the Debugger View displays a message that reads: "Connected with Mule. Waiting for a Mule message to arrive!".
Additionally you can run your application in debug mode by right clicking in the canvas and selecting the Debug Project option, or by clicking the Debug button on your top toolbar