From Bandaranaike there are choices of either bus, Tuk Tuk or taxi which will take you to Colombo Fort railway station where you can catch a direct train to Mirissa. A quicker option is to catch the highway express bus which you will find at the bus stations which is around the corner from the train station. This bus will take you to Matara then you will catch another local bus or Tuk Tuk to Mirissa. The bus will stop just across from Sunanda Road where you will find the hostel the the beginning of the road. Another option is to catch a taxi straight from the airport to the Hostel, w high we would organize for you In advance (about 47USD).