I would like to begin by saying that God makes His desires known. He does not give all the details, nevertheless, He does make His will known to His people - both individually and corporately. The Bible record proves this time and again.
God told Adam and Eve, not to eat of a specific tree in the garden. God told them to multiply and fill the earth. God instructed Cain and Able how to sacrifice. God walked with Enoch and no doubt He communicated His will to him. God told Noah to build an ark, and even how to down to the last measure. He told him when to close the door. God told Noah to multiply and to replenish the earth. God told Abram to leave his own country and kin, and to go to the land of promise... and on, and on. Then at the very end of the Old Covenant period God told Zachariahs that Elisabeth would have a son and that his name would be "John." God told Mary that she would bear a Son through whom salvation to mankind would come. God told Joseph through a dream to marry Mary and to take her to Bethlehem, where she would ultimately give birth. God spoke clearly to His Son Jesus Christ, and our Lord made ever-so-clear that He did ONLY what the Father told Him to do, and that He said ONLY what the Father told Him to say. Jesus told His disciples to go wait in an upper room until the Promise of the Father would come... and on, and on. Then with the apostles and other New Testament believers God inspired and anointed Peter to preach in the first open-air gospel message. Later God spoke through Stephen in the first very specific, open-air rebuke of religious leaders for their rejection of God's Spirit after the Spirit had been poured out. God spoke to Phillip through an angel that he should "go south." God spoke to Paul and called him "to be an apostle to the Gentiles," and Peter to be an apostle to "the Jews." The Spirit continued to speak and God spoke through angels and through the members of His body then... and He still does today. He was not a deaf and dumb God then and He is not now.
The short answer to your valid question brother, that we have all asked at some time or another throughout the centuries of Christianity is - that God will tell you His will to a certain degree and as you walk out what you do know He will reveal more. Suddenly at some point along the way you will understand where He was taking you all along.
God speaks to His people. The problem is that our listening is distorted by a number of things. One, we may not think that God still speaks so we don't know to listen. Two, we believe so many things wrongly about God that we are confused in our heads about what He might be saying concerning His will for us. Third, we are not accustomed to hearing His voice so when He speaks we are unsure whether it is really Him or not.
Finally, for real-life illustrations to accompany this brief answer on such an important subject. The Spirit of the Lord told me to go south one time. I got on an airplane and went south. He unfolded our ministry call from there. He spoke to me ten thousand times from there and still does. He spoke to me one time to get on a plane and to fly west a thousand miles to a strange city and that He had an appointment for me there. I did, and He did. He spoke to me to go to the Middle East and I sat waiting until two weeks later He gave me tickets to fly there. From there he opened up that part of the world. He spoke to me to get in my car and to drive west and I did. I had a tank of gas and two hundred dollar, and my wife with me. We went as far as you can go west in a car and returned several weeks later with more than five thousand dollars and after having ministered the word of God strategically in many places. I knew no one west of Dallas, TX at the time and had only one contact going west who was not even present when I arrived. The Lord did it all. Through my positive response to His simple command for that single illustration, I ministered to hundreds of thousands of believers, producing much fruit without the slightest bit of striving for the next several years.
I could tell story, and story, after story, after miracle, after miracle. This is not because I am anything but saved by His grace and like everyone else who is saved, I am called to do His will and He fulfills His responsibility to tell us what His will is. I have learned to hear His voice through His grace given to me by abiding in His word, abiding in prayer, and by honestly desiring to do His will.
You can too, brother and sister. You can too.