There are two easy ways that I know of:
Make sure the channel is in you favorite list, right click select "edit" and change the video PID to 0 (if you want you can set scrambled to FTA, but you do not have to) and click ok. Close the DVB World program and restart it. The channel will now show up as an audio channel.
The second way does not require the program to be restarted. Go to the the favorite list and right click the scrambled video channel and select "Add a New channel". Change the video PID to 0 (if you want to you can set scrambled to FTA, but you do not have to) and click ok. Now find the newly created audio channel and select it.