What are we required to do with the mysteries once we understand them?
Once believers understand the mysteries, they are required to be faithful stewards by passing them on to others, especially those who have never heard or know nothing of them. The mysteries are not to be kept privately; they are to be managed and shared faithfully.
Les explains from 1 Corinthians 4 that Paul puts a responsibility on believers of this age. A steward is a caretaker, manager, or overseer, and it is required that a steward be found faithful. Since no one can manage or share what they do not know, believers must study and learn the mysteries. Once they get a hold on these mysteries, they are to be faithful in passing them on to those who have probably never heard or who know nothing of them. Les also notes that Paul is dealing primarily with Gentiles, and these truths are to be administered faithfully.
Moreover it is required in stewards, that a man be found faithful.