The commissioning of the first "Missionaries" happens in Antioch. In reading Acts, up to this point the targeting of certain areas and populations (Jerusalem, Judea, Samaria, to the ends of the Earth) appears to be somewhat random (if following the leading of the Holy Spirit could be called random). Now, in Antioch, the Holy Spirit reveals to the leaders that two men should be set aside and sent out to preach in new areas the Good News about Jesus. They set aside Saul and Barnabas who took John Mark along as an assistant. Notice that the first place they sail for is Cyprus. Why, we ask, would they go to Cyprus first? The text gives no direct clue except the note in chapter 4 that Barnabas' given name is Joseph and that he is from Cyprus. This is "home coming" evangelism at its finest. The first place any of us should bear witness to our faith in Christ is in our own homes and among our own people. I will admit that this is also one of the hardest places to bear witness to the faith -- among those who knew us when . . .
After preaching in Cyprus, the Apostles go out and preach and teach in Perga in Pamphylia and then Antioch in Pisidia (yes, another Antioch). Here in Antioch of Pisidia we get the fullest example of a St. Paul sermon beginning at verse 16. It is typical of all the sermons we read about in Acts given to Synagogues: 1) God spoke to our ancestors; 2) God raised up leaders; 3) God sent John the Baptist; 4) the religious leaders in Jerusalem did not recognize the Christ of God when he walked among them and had him crucified; 5) But God raised him from the dead and appeared; 6) put your faith in Jesus and you will be saved. Many in the synagogue became Christ followers -- when Paul and Barnabas are kicked out of the Synagogue they preach to the gentiles and many more come to faith in Christ.
When Paul and Barnabas are forced out of Antioch of Pisidia they shake the dust off their feet and proceed on to Iconium. Notice in verse 13 that John Mark leaves Paul and Barnabas and returns to Jerusalem -- this leaving by John Mark becomes a point of contention between Paul and Barnabas later in Acts.
NOTE: did you notice that Saul of Tarsus has undergone a name change to Paul in your reading? As I understand it Jews who lived away from Jerusalem (such as Saul in Tarsus) were in the habit of using two names. One, their Hebrew name, and the other for commercial and public purposes. Saul, carries the name of the first king of Israel one Saul son of Kish. In the Gentile world he is know by the Latin Paulus or Paul.See verse 9 -- Saul, also known as Paul . . . from that time on Luke only uses the Paul to refer to him. All subsequent uses of "Saul" come when Paul is telling the story of his own conversion.