Paragraph 4. The Lord Jesus Christ is the Head of the church, in whom, by the appointment of the Father, all power for the calling, institution, order or government of the church, is invested in a supreme and sovereign manner...
Paragraph 5. In the execution of this power wherewith he is so intrusted, the Lord Jesus calls out of the world unto himself, through the ministry of his word, by his Spirit, those that are given unto him by his Father,9 that they may walk before him in all the ways of obedience, which he prescribes to them in his word.10 Those thus called, he commands to walk together in particular societies, or churches, for their mutual edification, and the due performance of that public worship, which he requires of them in the world.
Paragraph 7. To each of these churches therefore gathered, according to his mind declared in his word, he has given all that power and authority, which is in any way needful for their carrying on that order in worship and discipline, which he has instituted for them to observe; with commands and rules for the due and right exerting, and executing of that power. (What power? The power of calling, institution, and order.)
Paragraph 8. A particular church, gathered and completely organized according to the mind of Christ, consists of officers and members; and the officers appointed by Christ to be chosen and set apart by the church (so called and gathered), for the peculiar administration of ordinances, and execution of power or duty... (Again, what power? The power of calling, institution, and order.)
Paragraph 9. The way appointed by Christ for the calling of any person, fitted and gifted by the Holy Spirit, unto the office of bishop or elder in a church, is, that he be chosen thereunto by the common suffrage of the church itself...
Paragraph 10. The work of pastors being constantly to attend the service of Christ, in his churches, in the ministry of the word and prayer... (Why should they attend the churches in 'the ministry of the word'? Because that is where the power of calling lies.)