It's probably better if you explain why you can't connect...
JDeveloper allows you to set-up connections (to DB, AS, SOAP server etc), and provides wizards to do so. They are pretty straight-forward.
However... you need to know the App Server log-in (usually ias_admin) and password. And, you need to know the OracleAS home directory because remote deployment involves the use of a server-side utility called DCMCTL. Also, you need to know the admin port (usually 1810).
Finally, if you're using EJBs then you need to set up the RMI connection info. All this stuff should be available from your sys-admin.
If you want to connect to the "standalone OC4J" conatiners built into JDeveloper, the log-in info is "admin" and "welcome" if I recall correctly.