[Q] Android Studio build error - Google Drive topic

I'm totally new to android Dev.

I'm trying to create an app that can access Google Drive. I have done all the developer setup on the Google console.
I used SDK manager to install google play services etc.

For some reason I'm getting the following error:

cannot find symbol variable mGoogleApiClient

mGoogleApiClient = new GoogleApiClient.Builder(this)
.addApi(Drive.API)
.addScope(Drive.SCOPE_FILE)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.build();


I'm missing a library or something. Can anyone suggest why this would be?