Hello
Everything is explained in the plugin
Where are you using it (article, module VM,Kunena)? Joomla version?
Explain what you're doing so we can tell what you're doing wrong
To me the best modus operandi to test would be
Code:
{ http://soundcloud.com/subjex }
without spaces after and before accolades
Code:
{http://soundcloud.com/subjex}