Two-way Google Calendar sync lives under Availability → Calendar Settings — not under Preferences, which is easy to mix up since both relate to scheduling.

Once connected, your Wise sessions sync to your Google Calendar, and existing events on your Google Calendar are factored in when checking for conflicts (see Understanding and resolving session conflicts). This is worth setting up if you already rely on Google Calendar day-to-day, since it keeps everything visible in one place rather than requiring you to check both.