Google Calendar and Forecast

I am unable to find a way to link my calendar (google apps). I have tried to copy the link into my google calendar, but it does not populate my forecast.
There are several things I am unsure about:

  1. How do I not have the Mac calendar as my default calendar?
  2. How do I activate my calendar so that it will link to Omnifocus.
    I am sure it is something simple … but I just can’t get it figured out.
    Thank you fort our help!

You’ve got to link your Google Calendar with iCal and OmniFocus will connect to your iCal automatically.

http://imgur.com/a/g09lG#0 <= Here’s how

Thank you, I have tried that and all calendars are linked, but I still don’t have a calendar on my forecast.