Hi,
      The prompts from prompt management are stored in URL http://<ipAddress>/appadmin/temp/xxx.wav
Follow the below steps:-
1)Create A Editor script to play this prompt having the script steps include a)CreateURLDoc Step containg the URL of vxml say playAudio.vml (find below) b)CacheDocument c)VoiceBrowser Step
2)Create An Application and associate to this script with a trigger
3)Dial the trigger 
4)The prompt will be played
 
#The VXML playAudio.xml
<?xml version="1.0" encoding="UTF-8"?> 
<vxml version="2.0" xmlns="http://www.w3.org/2001/vxml" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://www.w3.org/2001/vxml 
   http://www.w3.org/TR/voicexml20/vxml.xsd">
<form>
<block>
<audio src="http://<ipAddress>/appadmin/temp/xxxx.wav " />
</block>
</form>
</vxml>