Different people were sent out in different ways. Sometimes we may wish for a clear, direct command that includes all our desired details. But God does not always reveal the future to us. He may work with us through methods that we find to be uncomfortable. In each varied case, what is most important is to understand God's leading and to have confidence in Him.

God told Abram to go, but did not tell him where to go.

Now the Lord had said to Abram: “Get out of your country, From your family And from your father's house, To a land that I will show you. Genesis 12:1
By faith Abraham obeyed when he was called to go out to the place which he would receive as an inheritance. And he went out, not knowing where he was going. Hebrews 11:8

God sent Moses to Pharoah around the age of 80. This was a direct call after Moses had spent many decades in God's school of preparation.

Come now, therefore, and I will send you to Pharaoh that you may bring My people, the children of Israel, out of Egypt. Exodus 3:10

God sent Jonah, and specified the name of the city where he should go.

“Arise, go to Nineveh, that great city, and cry out against it; for their wickedness has come up before Me.” Jonah 1:2

Now there was a certain disciple at Damascus named Ananias; and to him the Lord said in a vision, “Ananias.” And he said, “Here I am, Lord.” So the Lord said to him, “Arise and go to the street called Straight, and inquire at the house of Judas for one called Saul of Tarsus, for behold, he is praying. Acts 9:10-11

And a vision appeared to Paul in the night. A man of Macedonia stood and pleaded with him, saying, “Come over to Macedonia and help us.” Now after he had seen the vision, immediately we sought to go to Macedonia, concluding that the Lord had called us to preach the gospel to them. Acts 16:9-10

Joseph

But now, do not therefore be grieved or angry with yourselves because you sold me here; for God sent me before you to preserve life. Gen 45:5
And God sent me before you to preserve a posterity for you in the earth, and to save your lives by a great deliverance. So now it was not you who sent me here, but God; and He has made me a father to Pharaoh, and lord of all his house, and a ruler throughout all the land of Egypt. Genesis 45:7-8

Therefore those who were scattered went everywhere preaching the word. Acts 8:4

Now the Angel of the Lord came and sat under the terebinth tree which was in Ophrah, which belonged to Joash the Abiezrite, while his son Gideon threshed wheat in the winepress, in order to hide it from the Midianites. And the Angel of the Lord appeared to him, and said to him, “The Lord is with you, you mighty man of valor!” Judges 6:11-12

God's call to Elisha came through another prophet, Elijah.

So he departed from there, and found Elisha the son of Shaphat, who was plowing with twelve yoke of oxen before him, and he was with the twelfth. Then Elijah passed by him and threw his mantle on him. 1 Kings 19:19

Now when they had gone through Phrygia and the region of Galatia, they were forbidden by the Holy Spirit to preach the word in Asia. After they had come to Mysia, they tried to go into Bithynia, but the Spirit did not permit them. So passing by Mysia, they came down to Troas. And a vision appeared to Paul in the night. A man of Macedonia stood and pleaded with him, saying, “Come over to Macedonia and help us.” Now after he had seen the vision, immediately we sought to go to Macedonia, concluding that the Lord had called us to preach the gospel to them. Acts 16:6-10

Then I said, “I will not make mention of Him, Nor speak anymore in His name.” But His word was in my heart like a burning fire shut up in my bones; I was weary of holding it back, and I could not. Jeremiah 20:9

Now in the church that was at Antioch there were certain prophets and teachers: Barnabas, Simeon who was called Niger, Lucius of Cyrene, Manaen who had been brought up with Herod the tetrarch, and Saul. As they ministered to the Lord and fasted, the Holy Spirit said, “Now separate to Me Barnabas and Saul for the work to which I have called them.” Then, having fasted and prayed, and laid hands on them, they sent them away. So, being sent out by the Holy Spirit, they went down to Seleucia, and from there they sailed to Cyprus. Acts 13:1-4

For if you remain completely silent at this time, relief and deliverance will arise for the Jews from another place, but you and your father's house will perish. Yet who knows whether you have come to the kingdom for such a time as this? Esther 4:14