Ok, wait some time.
If have time, I will make the simple tutorial more readable.
No it does not work with phonegap build service.
But I recommed you to use xdk. (works on xdk (crosswalk))
Xdk is more easier to use.
You can save captured screen image to SD file by using Phonegap ScreenCapture.
And then upload to your server (http) by using Phonegap FileTransfer.
Finally, you can share the uploaded image by using ShareApp.
Exactly these 3 plugins are needed for you.