You are able to sync Skedda with external calendars such as Google Calendar, Outlook, iPhone etc. by using your account's dedicated iCalendar link. Note that this feature is exclusive to venues subscribed to an appropriate paid plan (see the Your Skedda Plan section in your Venue Profile).
Also note that, as most external calendars don't share and respect many of the concepts that Skedda does (e.g. minimum booking times, booking windows, lock-in times, dependencies between spaces, and pricing), the sync is a one-way, read-only feed (from Skedda to the external calendar). That is, Skedda does not support two-way syncing to/from external calendar applications. Practically this means that you can't create bookings in an external application and have them reflected in Skedda.
You can find your venue's iCalendar link by going to Settings > Venue Profile and then going to the Integrations section. This section contains the link under the title 'Feed to external calendars'.
Depending on your client application (Outlook, Google Calendar etc.), you'll just need to copy and paste the link using a function in the direction of "Add by URL" or "Add external calendar". Here's a concrete example of this option in Google Calendar:
Once added, your client will automatically fetch updated booking information from Skedda periodically. The update interval varies between client applications. For Outlook it is typically of the order of 10 minutes or so. In the particular case of Google Calendar, note that this can refresh interval can be longer (of the order of a few hours - something that Skedda cannot control).