There are those that are used in the simple gift of prophesy that will have an anointing from the Lord and in time begin to prophesy regularly. They will find themselves moving in this gift and in time it will develop into prophetic ministry. You will become much more sensitive to His voice and the leading of His Spirit and find yourself growing and stepping out in faith often. God speaks to each one in different ways. In my own life the Lord would show me a picture of something before I prophesied. Sometimes He gave me a simple thought or sometimes a few words. As you step out in faith He will fill your mouth. This can be in a meeting, on the street, or at home. There will come a time that you may start to speak things more directionally. The quickening of the Holy Ghost will come upon you and you may quickly sit down and type out what the Lord was speaking to you for His people. This is especially true in online prophetic ministry. These will be wonderfully used of God as is anyone speaking a Word for Him.