In general, the basic setup instructions for Orca currently are as follows:
Verify gnome-speech is working
Verify gnome-speech is working by running the "test-speech" application. If you cannot get this application to speak, then Orca won't speak.
Get BrlTTY working
If you want to use BrlTTY, get it setup and running before you configure Orca. When Orca runs, it will detect if BrlTTY is running and will use it if possible.
Run orca --setup then log out and log back in
'orca --setup' will run a configuration UI to allow to set up your preferences for Orca. This also sets a needed configuration property to enable accessibility for the entire desktop. You need to make sure you log out and log back in for this property to take effect.
The 'orca' command starts Orca.