The Jetspeed Control Panel is available at [JETSPEED_ROOT]/screen/Admin. After installation you should change your logon and password within JetspeedResources.properties.
The Control Panel should give you access to most runtime configuration parameters within Jetspeed. The most importantant are the Memory Store and Content Feed panels. With these you can look at your cache usage and clear your cache if you want. The Content Feed panel will allow you to manually refresh your OCS content feeds.
Developers that want to add Portlets within Jetspeed should also provide a Control Panel. In order to install a control panel item you would implement it as a Portlet and then add a property to JetspeedResources.properties. You should see a line of that begins with "admin.portlet.classname". Juet add another line with your new Portlet and you should be done.