How does 'Android Lost' application work? its very urgent and important for me.

Lost my android device. Now I have come to know that its being used and is online. By checking the Android Robot symbol in my friends chat list meaning, that my gmail account is logged in the android device. And What I did is installed 'Android Lost' application from play.google.com from the browser, and it shows its installed. But not knowing how to use the app to get the gps location from the device. Obviously the mobile number (sim) is a different one. Any useful apps to track it down?

-Update 1-

Logged in at http://www.androidlost.com/ with google credentials.
But the problem is it asks for the device to be registered.
 1. Don't have direct access as it is lost.
 2. Cannot invoke the app by sending commands via sms. (As the sim is disabled/replaced with new one)
Using Android-lost is easy;


Install android lost from gPlay or Google Play (You already did this)
go to the Homepage of Android Lost
Log in using your Google Account!
Use all the nice features, let your phone ring, locate it, erase all your data or change the pin, give the thieve or finder a message etc.