CAR 
Though I support public transport as a priority in environmental defense, your car is definitely the best option to get to Trisobbio. 
From wherever you're driving, target motorway A26 "Genova-Gravellona Toce" (toll required) and your exit is OVADA. 
Note: I can give you full route details from specific area/country. Just contact me before planning your route.
From Ovada follow panels Trisobbio (5Km). 
Enter the village and follow "Castle" (0,3Km) 
Final destination is Via Italia, 9
TRAIN 
Regional and domestic connections: target GENOVA BRIGNOLE station or GENOVA PRINCIPE station) or ALESSANDRIA. 
From these stations local trains operate to OVADA station. 
From the station public bus operates to downtown and from downtown coaches operate to Trisobbio 
Please contact me for full details.
PLANE 
Nearest airport is Genova Cristoforo Colombo (GOA) 
Milano Linate (LIN), Milano Malpensa (MXP) and Torino Caselle (TRN) are 1-1,5hour driving distance. Best option is to rent a car and drive to Trisobbio (see above section "CAR")
PARKING 
The apartment has no private-parking. You can comfortably embark+desembark luggage at the front door and park your car in a large public car-park, 50mts away