The MBean explorer view was originally a google code project which we took and expanded on quite a bit. It has no concept of actually starting the JMX server at all. You must start the server separately.
What the JMX server *can* do is connect to an already running mbean server if you know how to connect to it. This can be a jboss server or a non-jboss server. Basically if you wanted you could start a JMX server with a simple main class (JMX is pretty much standard in java now) and then use the view to connect to it.
I recognize there's no way to edit a connection and you're welcome to add a feature request for it in JIRA which we'd be happy to look at.
If you want to use it specifically with JBoss servers, however, thanks to some added hooks, if you go to the servers view or jboss servers view and create a JBoss type server (must be from the "JBoss Community" or "JBoss Enterprise Middleware" category, NOT the "JBoss" category) then a server will automatically appear in the mbean explorer.
If you then start the server in the servers view, once the server is started, the connection in the mbean explorer should be made and you should be able to browse the MBeans of the running jboss server.