How are we to do that if we don't know what that faith is?
We are told to "contend earnestly for the faith once for all delivered to the saints" (Jude 3).
It originated as an eastern branch of Syriac Christianity, and used the East Syrian Rite in liturgy.
It developed distinctive theological and ecclesiological traditions, and played a major role in the history of Christianity in Asia.
The church fathers, especially prior to the Council of Nicea, do not back up the Roman Catholic version of history.
This page assumes that you know that the Roman Catholic Church bases their authority on the teaching that Peter received universal authority from Jesus, then passed it on to the bishop of Rome.