First, you'll want to navigate to the four line horizontal menu and move to "Manage your Profile & Preferences." To utilize the RingCentral extension, this link here: Using the RingCentral Extension will provide a full overview.
Next, under "Integrations" you may "Link your RingCentral Account."
You'll then be directed to a pop-up where you may enter your email ID or phone number followed by your password to login.
With that complete, you'll then "Authorize" those changes.
With that "Authorized" you'll notice a RingCentral Extension located in the lower right hand corner of your screen. You may drag this wherever you'd like and you will need to sign in using your Ring Central credentials.