This will come naturally if you play as a Mage. You must have a Divine Magic Ring equipped to use spells.
You have to hit enemies 500 times cumulatively over all your battles. I got this around level 10. Using Shadow Missile
and Shadow Impact
I found spamming Shadow Missile to be the fastest way of grinding 500 hits as it fires off quickly, takes less magic and does less damage than Shadow Impact. Remember to use magic potions if you run low on Magic.