Once you have believed in Christ, you should go on to represent Christ on Earth. To be a witness is to be a living testimony/representative, example/evidence of Jesus Christ. We as Christians must daily let go of the flesh and be clothed with the nature of Jesus.
Witnesses are those who have received the gospel (Romans 10:10) and are constantly led by the spirit of God (Romans 8:14). They are usually not ashamed of the gospel of Christ, just like Paul, they fearlessly identify with and preach Christ. (Romans 1:16). Witnesses stand as a light in this dark world. They show light to the world, through their lives and character, they point people to Christ and teach people how to live like Christ.
Mathew 5:14 says we are the light of the world, but what are you doing with that light?
Are you letting it shine that the world may see and glorify God, or are you covering it?
Can people around you even acknowledge that you are a believer?
Let your light shine and help people around you know God genuinely through your life.
People will know you as a true witness of our Lord Jesus if you preach and defend the gospel; through your actions and reactions to issues; through your conversations and mannerisms; through your strong belief and faith in God; through the company you keep. You will grow more in the knowledge of our Lord Jesus and will be empowered to reflect Him when you diligently read, study and meditate on scriptures and by your communion with God in meditations and prayers.
Also, take heed to your self! 1 Timothy 4:16 says “take heed unto your self, and unto the doctrine, continue in them: for in doing this thou shall save thyself, and them that hear thee”.
Don’t be too confident and proud, learn from Christ, in the magnitude of His wisdom and power, He was meek and lowly (Mathew 11:29).
May we in words and in deeds be true Witnesses of our Lord Jesus Christ, Amen!