You should get an e-mail when you have booked through viator.com . I think Viator is just the online booking agent. The local transportation company is called "Holiday Services". The booth in Mobay airpost says "Holiday Services" I beleive. In any case, just follow the instruction in the e-mail and don't forget to re-confirm your arrangements a few days before arrival in MoBay and again a day before your depature from Negril. On my departure, I just went to the front desk of my hotel and asked them to call Holiday Services for me and they did. No problem.