The Centre - Location

The first option is to fly to Zürich airport. At the airport you can catch the train to Zürich mainline station and then a direct train Zürich to Bellinzona - Locarno. See schedules.
You can also fly to Milano Malpensa (Italy) and take the connection by bus to Lugano railway station; then you can take a train to Locarno.
From Locarno to Ascona you can go by bus no. 1. From Ascona (old post office) walk up the hill in the direction of Monte Verità/Hotel Ascona. The Centro Incontri Umani is behind Hotel Ascona, Via Signor in Croce 9.