Master Kerkir:
First, you will need the Soulshots themselves. I'll give you a couple. Once you equip a weapon Soulshots are equipped automatically.
There also exist Spiritshots, by the way. They make your magic more powerful.
Attacks enhanced with Soulshots deal way more damage, you'll notice it immediately.
Okay then. Equip Soulshots and attack the Training Dummies again.