How to start running queries in Oracle? I've just installed the last version of free Oracle (11 XE) and I would like to run some queries. I've also installed the DreamCoder IDE to connect to the Oracle but I cannot run any query. Already trying for 2 hours with no success.
The oracle service is already running.

In the new connection menu in DreamCoder asks for:

username: admin
password: ***


Now I have 2 options: 

First: TNS
Database: XE (it's already set by default)
Connect as: [normal, SysDba, SysOper, SysASM] I select the SysOper option.
Instaled clientes - Connect using: XE (the only option available)

Second Direct
Host name: localhost
Port: 1521
Database name: XE (from the TNS)


When I test the connection with the TNS I get connection successful; Then when I really connect I get:


  "NET: Invalid Host";


When I test the connection with the Direct: 


  "ORA-01017: Invalid username/password; logon denied"


I really don't know what to do more.
Because probably you haven't created an 'admin' user in Oracle yet. There's no built-in 'admin' user in Oracle DB. Try to connect as SYS "as sysdba", or maybe you need to run some prerequisite install procedure in your DreamCoder IDE.