Your RingCentral and Google contacts do sync and are easy to find from one easy to search screen in the plug-in that you will get with the RingCentral for Google for Work integration. It is a Chrome extension that you can get from the Chrome Web Store when you do a search for RingCentral. Once you enable the extension, and reload your Chrome browser, you will see the log in screen just as you would see for your RingCentral for Desktop application. Once you log in and select contacts, you will find both your RingCentral and Google contacts.
I have a Mac and this is the application I use when I am in Chrome and need to access my Google contacts.
If you have your Google contacts sync with the Apple Contacts application (done within System Preferences>Internet Accounts), and you turn on View Mac Contacts within the RC for Desktop app, that will show the Google contacts directly within the RC for Mac Desktop application.