The Gospel of John is sometimes a challenge to understand. In this gospel Jesus is explaining that He is the one who comes from above. And to demonstrate that this is true He has the testimony from John, the deeds He has done and the Holy Spirit through the graces of baptism. If you do not believe His words then believe Him through His deeds.
The method that Jesus developed can be broken down in to these two words: service and testimony.
Service, the act of developing a relationship with another. Taking the time to really know someone. How long does that take? You will know when they ask you a question about your faith. By you being real and authentic, living a virtuous life, people will respond because deep in their hearts that is the life they desire to live.
Testimony as how you can share your struggles to live that virtuous life. You do not need to embellish your words, just speak the truth.
The truth is that all of us struggle. As we admit we have vices and sins in our humility we discover all people do. And together, by working to learn the virtues and implement them in our daily lives, we can change our lives to be faith filled Christians. The first step is acknowledging our failings and that we cannot go it alone. Second step, develop a prayer life, read the Bible, and go to confession and Mass. Next step, start today.
May the Lord bless you in the name of the Father, and of the Son, and of the Holy Spirit. Amen