At the behest of Hrotha, you must speak with Aragorn, son of Arathorn, to gain the great wisdom of the Wardens.
'And to that, I will tell you as I have told the others: I know no secrets, or none that could be called wisdom. I trust my spear and my arm, my corselet and the strength of my heart. And perhaps that is the greatest lesson of our kind, to trust in yourself, the weapon you wield, and the armour you wear.
'Very well, then. That is where we shall begin, if you want. I will see you properly armed, and we will call that a kind of wisdom.'
Hrotha knows of a legendary warden who could teach you great lessons, but first you must be suitably outfitted.
Aragorn can be found in Rivendell, in one of the guest rooms of Elrond's House.
Hrotha counselled you to speak with Aragorn, the Ranger also known as Strider.