It is a stable principle that those who are ordained as elders [through fasting, prayer, and the laying on of hands] are men who are already doing the work of elders:  their service is what qualifies them, as it is the evidence of the Holy Spirit’s work and calling in their heart.  

Therefore, the apostles were simply recognizing and confirming God’s work when they ordained elders in every church (Acts 14:23), a fact that is evident in that they did so on their return trip to these cities:

And when they had preached the gospel to that city, and had taught many, they returned again to Lystra, and to Iconium, and Antioch, confirming the souls of the disciples, and exhorting them to continue in the faith, and that we must through much tribulation enter into the kingdom of God. And when they had ordained them elders in every…