To sync your Google calendar, go to Account Settings and choose "Calendars". Click the 'Connect Google Calendar' button and follow the prompts.
Please note: You can only sync ONE Google Calendar at a time in 17hats. Attempting to connect an additional google calendar will unsync any successful connections you already have. You can create and sync multiple sub-calendars through the 1 connection however. To learn about our workaround for connecting more than 1 Google Calendar using Sub-calendars, click here.
We do not currently support iCal/calendars app, but the video will provide instruction on connecting your iCal to a Google Calendar (OS X only).