Found the following in OAS documentation:
Accessing Application Server Control Console in Standalone OC4J
The Application Server Control Console is installed and configured automatically when you install the OC4J software. It is started by default when OC4J is started.
The console is accessed through the default Web site, which is configured to listen for HTTP requests on port 8888. To access the console, simply type the following URL in a Web browser:
http://hostname:8888/em
Doesn't work on my system for some reason. Will post back if I find out why.