Barnabas and Saul were commissioned by the church at Antioch to go on their first missionary journey. They were guided by the Holy Spirit.
Seleucia was the ancient seaport city of Antioch, about 20 kilometers (12 miles) west of the city at the opening of the Orontes River.
from there to Cyprus: Barnabas was from Cyprus, the next stop on their journey (4:36).