Android : Package name of android application

I am a non CS-IT B.Tech student & as i love programming i have opt for python language as my final semester training.I have built an android application based on python & kivy successfully. I am using "Python for Android - Builder" to generate apk of that app as i am using windows & i am not aware of any platform which will be used to generate apk of android application based on kivy. In "Python for Android- Builder" i am getting error in package name... Please give me some advice so that i can resolve this package name problem... Thank you all in advance for your advice...