it's not a good idea to revive old threads, they tend to not be relevant anymore.
The documentation was updated some time ago. Ensure you are using the following manual page C3 manual - Google Play. I say this as we've had some users end up looking at the documentation on scirra.com which is for Construct 2, and is often missing new features or incorrect for C3.
I don't believe we have a tutorial on using the Google Play plugin, but the documentation includes instructions on how to get started for both HTML5 and Android exports. If you have any specific issues ask on the forum, there's a number of active users on the forum who have experience with the plugin.