I don't think this is possible. Check your preferences to see if there is an option to enable your computer as an Airplay speaker. If it's not there it can't be done (at least not currently).
Supposedly 10.1 beta is bringing this functionality, so I should be able to answer this for you shortly.
Again, my only real complaint here is that the app doesn't handle an artist who has 1,000+ songs associated with them. It simply shows the album names and none of the songs for the albums, making it impossible to use properly.
