If you have two accounts with their own calendars (representing two separate businesses), but you want to sync the calendars together so that when a customer makes an appointment online for one company, their appointment will black out that time slot in the other company's schedule. Both businesses will have the same exact schedule, you would want to use one single Google calendar as your primary calendar.
Then, Sync that same calendar to both Setster accounts.
1. log into one Setster account , while logged into that Google calendar and perform the sync.
2. Log out of that Setster account and log into your 2nd Setster account.
3. Sync to that account.
All appointments will now show up on your primary google calendar from either Setster account.