You can use the start and stop buttons on the webMathematica Server view to start and stop your webMathematica server. When you launch the server the output from the server is displayed in the console view.
The information in the console can help to track down problems with running the server. For example, if a server is already running then a new one may not launch.
Note that in normal operation a server is run as a service launched by the operating system when the machine on which it runs is launched. However, when developing material for your server it is useful to have a tool such as this for starting and stopping the server and seeing the results of your work.