The Social Review Engine requires a Google Project Client ID and Secret Key in order to use Google Plus Connect for Review submissions much in the same way we use Facebook Applications. The only difference is the process which is required to obtain one and the proper settings.
Here is where you will insert these in the General Settings:
*This Step is required before you can use Google for Review Submissions.
Go to the Creating A Google Project With The Google API Console Knowledge Base page to see a complete step by step tutorial on how to create an Application for Google Plus.