Bishop Arias made his studies of secondary and philosophy in San Sebastian after which he entered into the Order of Augustinian Recollects. Between 1948 and 1952 he did his theological studies in the seminary of Our Lady of Good Counsel in Monachil, Granada and, later, received a diploma in spiritual theology from the Teresianum Institute in Rome (1963-1964).
Bishop Arias was ordained in 1952 on the occasion of the Eucharistic Congress held in Barcelona that year. Following ordination, he worked in various schools serving as priest and professor. Between 1952 and 1953, he taught Natural Sciences and Cosmology at St. Rita College in San Sebastian, Spain. Later, he taught religion in Maddox Academy in Mexico City. Upon his transfer to Kansas City, Kansas, and to the major seminary of the Monastery of St. Augustine of that city, he served as professor of religion and prefect of seminarians. He also taught Spiritual Theology, Church History and Psychology from 1964 to 1966.
In 1983, he was named Auxiliary Bishop of the Archdiocese of Newark, New Jersey engaged principally in the developing the Hispanic apostolate in the Archdiocese. He represented the Hispanic community in the northeast region of the United States and in various national congresses and encounters dedicated to the development of the pastoral aspects of this apostolate. As bishop, he served on various commissions, including, the Episcopal Commission on Communications, Hispanic Affairs, the V Centenary, and Latin America. He is a member of the Episcopal Conference of New Jersey and is a member of the Foundation for Hispanic Culture of New York. In the Archdiocese he also served as Regional Bishop of the County of Hudson, Episcopal Vicar for Hispanic Affairs, and Pastor of the church of St. Joseph of the Palisades in West New York.
The Archdiocese of Newark is the metropolitan see of the ecclesiastical province which includes the whole state of New Jersey which has a population of 9, 000, 000 and is divided into five dioceses. The Archdiocese of Newark is contiguous with the Archdiocese of New York separated only by the Hudson river and is divided into four regions or pastoral zones. It has a population of more than 3 million inhabitants of which one and a half million are Catholic. The hispanic population is around a half million. There are 240 parishes, 1000 priests, 1700 religious, 4 universities, 2 seminaries, 180 schools with around 60,000 students, 126 kindergartens, 8 hospitals, and 23 cemeteries. The Province of St. Augustine and the Province of St. Nicolas of Tolentine are present in this Archdiocese.