The two of them, sent on their way by the Holy Spirit, went down to Seleucia and sailed from there to Cyprus. When they arrived at Salamis, they proclaimed the word of God in the Jewish synagogues. John was with them as their helper (Acts 13:4-5).
The direction of their travel was determined by the Holy Spirit. Apparently, they did not preach until they arrived at Salamis, on the eastern coast of the island of Cyprus, about 130 miles from Seleucia. The population on Cyrus was predominately Greek, but many Jews lived there as well. The two pioneers began their mission outreach in virgin territory at the synagogues of the city.
The Holy Spirit had not set apart John Mark, but they took him along no doubt to help in numerous ways, relieving them of tasks and details that would have interfered with their important ministry of the Word.