Apartment was a little off the town main area where you could either take a bus to Fira or a bus to Kamari Beach (1.50 per person per trip). Need to walk around 10mins from the bus stop.
Main interchange is at Fira where you can change bus again to Oia or other areas. If you prefer somewhere more convenient and localised, stay in Fira instead.
Otherwise, Nick is a great host. He replies messages very quickly and provide assistance as much as possible. He provided us free pick up from the airport (about 5-10mins drive away) and arranged a taxi pick up to the airport (20 per trip).