You need to get off the train at Volovets station. Then you can get to the hotel by booking a transfer directly at the hotel or by local taxis, which are more than enough in the region.

Route Kyiv - Chop, to the village of Nyzhni Vorota, there will be a former traffic police checkpoint, turn left on it, then go through Volovets (there is one road) to Mezhyhirya, there will already be road signs indicating how to get to the hotel.