Take the bus bound for Shima Onsen from Nakanojo Station on the JR Agatsuma Line for about 40 minutes and get off at the last stop. It's a 15-minute walk from the last bus stop, but you can use the shuttle service if you book in advance.
Yes, free parking is available. Up to 5 cars can park in front of the hotel, and for 6 or more cars, you can use the Lourdes parking lot. It's on a first-come, first-served basis.
Check-in is from 15:00 to 20:00, and check-out is at 10:00. Times may vary depending on your accommodation plan, so please check each plan for details.