The way to do it is—if you clearly imagine the attack, shape, and power; use about twice the magical power than usual; and point your emotions at the enemy, the magic will be invoked.
If you compare it to normal magic, chantless magic comes out slower, has less power, and has larger magic power consumption.
It is a skill that is full of demerits. However, there are a lot of situations where you can't use normal magic, where you can't use your voice.
In those situations, whether or not you can use chantless magic means the difference between life and death.
That is why this is a required subject.