To find resources on patristic theology, select the Subject search on the Advanced Search of the catalog. For this particular subject, some of the search terms that will net you the largest number of relevant results are:
Church History--Primitive and early Church, ca. 30-600
Theology, Doctrinal--History--Early church, ca. 30-600.
In addition, you can search for works by and about the individual Church Fathers using their names as your search terms:
Origen. (author search)
Origen. (subject search)
Chrysostom, John, Saint. (author search)
Chrysostom, John, Saint. (subject search)
Augustine through the Ages by 
Reading Scripture with the Church Fathers by 
The Fathers Know Best: your essential guide to the teachings of the early church by 
Journey with the Fathers by 
Catena Aurea: Commentary on the Four Gospels Collected out of the Works of the Fathers by BR60-BR67- Christianity. Early Christian literature. Fathers of the Church, etc.
BR160-BR275- Christianity. History. Early and medieval.
BR1690-BR1725- Christianity. Biography.