expression, godan verb (-u)
use one's head; think; use one's brain
Encourages or describes thinking carefully, solving a problem mentally, or applying intelligence rather than brute force.
もっと頭を使えば、その問題は簡単に解けるよ。
If you use your head a bit more, you can solve that problem easily.
It's important to use your head, not just brute strength.