Google Calendar iCal import
This page gives a brief tutorial how you can find the icalendar link for your google calendar.
First, sign in to google calendar at https://calendar.google.com.
Now open the "General Settings" of any of your calendars:
In this dialog find the private address for your calendar and click on the 'iCal' button.
This will open a popup dialog with your private calendar URL. Select this URL and copy it into your clipboard. Now you can use this URL to import your calendar entries into WorkTrail.