Including 2 Outlook Calenders in Booking

Hi everyone, I have two outlook calendars - one private & one business. I would like to give my clients the option to book into free timeslots with me via Booking. However, Booking now only takes the appointments from one calendar. I would like to block all times - private & business - when I am not available for booking. The calendars are already synchronized with each other. Can you help me with this?

Many thanks in advance.