First, talk to Ak-Haranu. He will tell you that he has the manual, but will only give it to you if you bring him an oak shieldbow signed by Robin, the master bowman. Talk to Robin. He will refuse to sign the shieldbow, but will challenge you to a game of Rune-Draw. Win the game four times, and Robin will sign the oak shieldbow to repay the debt. Take the signed oak shieldbow back to Ak-Haranu to receive the translation manual.