Does your firm use a shared Firm Calendar? Only one user within your firm needs to sync their Account with the shared Calendar.
Depending on the user's Calendar you wish to use, just that person will need to establish the 2 way sync.
If you use a designated "Firm Calendar" your Account Manager can give you access to that account. Once your Log in as the "Firm Calendar" user, you can then establish the 2 way sync, which everyone will have access to. For more information, please reach out to your Sales Executive or Customer Success Manager.