Types--the typical sense--are discovered in the New
Testament, or in the agreement among "faithful people"
faithful to what was handed down to them--the Fathers
of the Church, in worship-- the liturgy--and its development
through the ages, in the documents of the Church, etc.
The Catholic Church believes that the Holy Spirit is a revealing
authority in the Church and reveals Himself to "faithful people"
in all ages.
The other criterion
for discovering the typical meaning of
Scripture is understanding that any type found in the text of
the Bible has to be related to the anti-type (e.g., Christ to
Adam). This confirms that God planned the relationship
of the type to the anti-type.