Integrate android eclipse project in unity3d

Hello friends..

I am learning unity.. So i have no idea about how do i use android project in unity..

I have implemented google+ play service api in my android eclipse project.. In that i have share button to share text on google+ account.

But my problem is that now how do i integrate my this android project with unity3d??

I have read http://docs.unity3d.com/Documentation/Manual/PluginsForAndroid.html.

But i am not getting clear idea. So please guide me . From where do i start and which steps do i need to perform?

Thanks for your support and help..