If your friend was part of the Armenian Catholic Church, which is in communion with Rome, then he can continue on as normal.
If he was part of the Armenian Orthodox church, which is not in communion with Rome, (although they have valid orders), then he should be received formally into the Church. It is a matter of renouncing the heresy of schism which separates the churches away from the seat of Peter, the Pope, the successor to the chief among the Apostles, and insurer that we are in Christ's One visible Church.
Disclaimer: I say that with full knowledge that the current Pope is acting/working very hard to undermine that very doctrine. I am not a fan of the Francis pontificate, though I pray for him everyday. Despite the controversial and anti-unifying character that he is, he is the sign of the Church that Christ founded on the Rock of St. Peter.
For better, and sometimes the worse, like these days, it is the true home for all Christians.