Sing to the LORD, all the earth. Proclaim His salvation day after day. Declare His glory among the nations, His wonderful deeds among all peoples. 1st Chronicles 16:23-24
All questions aside, the fact of the matter is, as a believer, you are called to spread the good news unless The Lord tells you otherwise. We do not all do the same thing or play the same roll when it comes to spreading the word, but it is our duty.
Winning a war in a battle field involves multiple players with different roles for the war to be won. There is the commander, the soldiers/warriors, there are snipers/archers, the armourer, the people who bring food to the battle fields (a great example is David when he took food to his brothers 1Samuel 17:17). We can even delve deeper and see how each of these roles play into our battle for the Kingdom of God. We obviously know that Jesus Christ is the commander, but where do we as believers fall? We have the soldiers who risk their lives on the ground; in our case, those will be the missionaries who leave their homes and loved ones behind to spread the gospel in foreign lands or across cultures. Then the snipers, those are long distant combatants whose job is to provide detailed surveillance from a hidden point, those would be our prayer partners; praying for those in the field constantly (Ephesians 6:18) for our war is not of the flesh (2 Corinthians 10:3). There is the armourer, whose job is to make and repair the soldiers’ weapons and armour, in the case of missions those are the pastors and fellow believers whose job is to uplift and to admonish those in the field (Hebrews 10:24-25). Then there is the one who brings food to the battlefield; in our case they are the donors, those who donate money and gifts in kind like medical supplies, food, farming materials and many more. All these people come together to fight the war for the Kingdom. All of us playing an important role, none can succeed without the other and the crowning jewel is Jesus Christ our Commander in Chief giving us graceful marching orders and the Holy Spirit equipping us with knowledge of the battle plan, guiding our steps with strength to face the enemy.
So, it is not really how to become a missionary but where in the battle does the Lord want you, what is your role. Prayer will guide you. The Lord will open your eyes to where you should be if you are willing. Fellow believers, let us go to the presence of God and ask where He wants us to be and how He wants us to help. For our commander has given us a command…
Therefore go and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit, and teaching them to obey all that I have commanded you. And surely, I am with you always, even to the end of the age.” Matthew 28:19-20
But you will receive power when the Holy Spirit comes upon you, and you will be My witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.” Acts 1:8