You should be at least LV5 before he takes you in as a student. For more information about different masters, kindly refer to the Masters Basics page.
00. Become Krillin's Apprentice
After this, you'll learn the strike skill "Super Attack Orin Combo"
01. Martial Art Mix
After this, you'll learn the ki blast skill "Destructo Disc"
Item Request
Bring him an Energy Capsule S afterward to receive the Z Soul: "I'll show you the results of my training!!"
02: Smash! Orin Combo
Unlocked Skill: Evasive Skill - Spread Shot Retreat
You have to equip the Orin Combo skill and finish him off with it.
03. Mastery
Unlocked Skill: Ultimate Attack Scatter Kamehameha
You have to equip the Destructo-Disc skill and finish him off with it.