Thanks for the question; I'm glad you wrote in.
The (JWs) Jehovah's Witnesses are an errant cult-like institution, and while their members seem to know the Bible, they do not, because they only know a particular method or script to convince people of their true religion but it is based on grave Biblical mis-translations that are not accepted by scholars, Catholic or Protestant. The New World Translation they follow is a deception, and it would take much ink to explain all the details of that. You should be careful not to get ensnared by the deception they all follow, so break off the talks until you have studied up and know the real biblical truth to refute them. Baptism is the tip of the iceberg; the divinity of Christ, the Trinity, the Sacraments, literally every aspect of the Faith is heretical.
Here is the truth: Jesus Christ (who is God, Second Person of the Holy Trinity, which they deny) came, started His Church with Twelve Apostles; He made Simon the leader when he dubbed him Peter (the office which is kept by the Pope), gave the great commission to baptize in the name of the Father, Son and Holy Spirit (c.f. Matthew 28). The Church has followed the precepts Christ gave from the beginning and there is 2,000 years of history to prove it. The formula for how to perform Baptism, its effect, meaning and purpose have been constant teaching throughout all of Christian history, and any serious review of the facts, will dismiss the contrary.
I have personally engaged with JWs only to find them breaking off any dialogue when they are seriously met with a legitimate challenge. They are taught not to accept literature from anyone while propagating the Watchtower pamphlets all the while (classic cult protectionist tactics). You will never see a JW in a formal debate anywhere, especially in a formal public setting, about any biblical issue because they would be shredded.
If you have a real friend who is in this cult, let him know that if he wants to be saved, he needs the true Christian Faith, the Catholic Faith, and true Baptism, not the falsified one the JWs peddle.
Start learning about these issues first. Read a few books, get equipped. One example is Catholicism and Fundamentalism by Karl Keating, a useful start for any apologetics. Then get something that deals specifically with JWs like:
Here is the TEXT version for the above graphic.
- Reasoning from the Scripture with the Jehovah's Witnesses by Ron Rhodes.
- The Catholic Answer to the Jehovah's Witnesses by Louise D'Angelo.
- How to Rescue Your Loved one from the Watchtower by David A. Reed.
- Jehovah's Witnesses Jesus Christ and the Gospel of John by Robert M. Bowman Jr.
- Scripture Twisting: 20 Ways the Cults Misread the Bible by James W. Sire.
- Jehovah's Witnesses Answered Verse by Verse by by David A. Reed.
Lastly, you can search our database for more on baptism as we have taken questions of a similar nature before.