We don't.
(I don't think the Protoevangelion is considered even an "ECF piece".)
First by comparison with what was received/always taught. Then, if the disagreement remains and is spreading, through a Council of all of the bishops (each having one vote). Then at the next Council, the earlier Council is either approved or rejected.
Some of Origen is "accepted", but some of his writings are condemned. Mostly, he worked on the first "parallel Bible", lining up all the different available versions.
A lot of what Origen taught was overidden. The Church, as before, judges by what was always taught and also "mindset"; what is called the "mind of the Church", the character - it's Christ centerdness. We have no infallible Pope.
After a while of reading the ECFs, you notice that they mention an earlier author (usually an ECF) and continue discussing that idea. They usually only mention the last author to state the idea, but you can generally follow teachings back to very early on this way. The earliest speak of what they have received.
So it is a pick and choose sort of thing, but based on a standard. Some writings are accepted, some discarded (or condemned), some kept but not as dogma or doctrine.
Just using what Standing Up is showing, thats what I am interested in.
No way is an ECFs word equal to God - Scripture is called the "Crown of Tradition" (and the Gospels are sort of like the "Crown" of Scripture). If an ECF is wrong, he's wrong. They're just human. But we recognize the Holy Spirit working in and through people, and and of course the working of the Holy Spirit is for the benefit of the whole (as in Paul's letter to the Corinthians).
The Protevangelion is not considered as Scripture (or even like an ECF). And the ECFs vary in opinions on many matters. As long as these matters do not negatively affect salvation, or are clearly wrong in some way, then they can be used for study, etc.
Never equal to Scripture (we kiss the Gospels, but no other book

).
So some things are relevant, some important, some interesting, and some dangerous (like some of Origen's teachings). The dangerous writings are "tossed out".