Keep going - it’s in the next section.
“Only be careful and circumspect in regard to whom you would confess your sins. Test first the physician to whom you would expose the cause of your illness. See whether he knows to seem weak with one who is weak, to weep with one who weeps, and whether he is acquainted with the art of consoling and comforting. Finally, when he has shown himself to be a physician both learned and merciful, do whatever he might tell you and follow whatever counsel he may give. If after much deliberation he has understood the nature of your illness and judges that to be cured it must be exposed in the assembly of the whole church, follow the advice of that expert physician, and thereby others may perhaps be able to be edified, while you yourself are the more easily healed.”
From this, I deduce that Confession was made privately to the priest first, and then, only on the advice of the priest, confessed publicly to the whole assembly during the Penitential Rite at Mass.
So, the custom of making public confessions during the Penitential Rite has since been replaced with the Confiteor, (“I confess …” recited in unison) but the custom of private confessions to the priest beforehand was already in place, even at the same time that we still had the public confessions.