The suggested way to add new commands to the console is to derive a class from the CommandConsoleBase class and in the InitializeCustomCommands() method, which is called during initialization by the base class, add your new commands and connect them to their appropriate command handler. For example:

// In Your Derived Class
public override void InitializeCustomCommands()
{
    AddCommand( new CmdObject( "kill", "Immediately kill the player", CommandConsole_Kill ) );
    AddCommand( new CmdObject( "nuke", "Immediately kill all on-screen enemies", CommandConsole_Nuke ) );
    AddCommand( new CmdObject( "degreelessness", "Toggle degreelessness mode", CommandConsole_Degreelessness, true ) );

   return;
}

The above example adds three new commands to XNACC:
There are other ways of adding/modifying commands and their behavior, which is covered in more detail on the Hooking Command Execution page.