There is many articles about how to test Push Registry with sms, here will give some hints how to test it in WTK.
I. Edit *.jad configuration
MIDlet-1: appname,/app.png,com.easywms.midlet.midletClass
MIDlet-Permissions: javax.microedition.io.PushRegistry
MIDlet-Push-1: sms://:50000, com.easywms.midlet.midletClass, *
or MIDlet-Push-1: sms://:50000, midletClass, *
II. The app must be install via OTA in WTK, this is required for WTK Push testing