Acts is the premier book for us to learn what the apostles were commissioned to do in evangelism. Luke begins Acts by telling us that they were commissioned to be witnesses unto Christ:
Acts 1:1 The former treatise have I made, O Theophilus, of all that Jesus began both to do and teach, 2 Until the day in which he was taken up, after that he through the Holy Ghost had given commandments unto the apostles whom he had chosen: 3 To whom also he shewed himself alive after his passion by many infallible proofs, being seen of them forty days, and speaking of the things pertaining to the kingdom of God:
4 And, being assembled together with them, commanded them that they should not depart from Jerusalem, but wait for the promise of the Father, which, saith he, ye have heard of me. 5 For John truly baptized with water; but ye shall be baptized with the Holy Ghost not many days hence. 6 When they therefore were come together, they asked of him, saying, Lord, wilt thou at this time restore again the kingdom to Israel?
7 And he said unto them, It is not for you to know the times or the seasons, which the Father hath put in his own power. 8 But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth.
As witnesses unto Christ, they were commissioned to tell people what they themselves had seen and had heard concerning Christ. Luke plainly tells us that Christ Himself showed Himself alive to them repeatedly over a 40-day period in many appearances to them. Acts 1:1-8, therefore, indisputably teaches us that Christ commissioned the apostles to witness to people that they had seen Him alive in those appearances and heard Him speak to them.