You just need to make sure that you add this entry:

     <Launch.Addon>
           <Name>Captain Sim 520 Menu</Name>
           <Disabled>False</Disabled>
           <Path>Captain_Sim\520\cs.sound.dll</Path>
     </Launch.Addon>

to P3Dv2 DLL.XML file.

Enter this %AppData%\Lockheed Martin\Prepar3D v2 in the Run command and the folder will open. Make sure you open the DLL.XML file (I use Windows Notepad), and not a backed up version of the DLL.XML! Then add the entry directly above the last line in the file (which is </SimBase.Document>), then save it. With Vista, Win7 & Win8/8.1 you might need to run Notepad as an administrator to be able to save the modified DLL.XML file.

If you really get stuck, email your DLL.XML file to me and I will add it for you, and email it back to you so you can overwrite the original. ;)