To display or make effective use of one’s power, ability, or skill; the demonstration of capability in an actual situation (often used as 'to exert' or 'to demonstrate').
試合で実力を発揮して勝利した。
He demonstrated his ability in the match and won.
彼女は新しい職場でリーダーシップを発揮した。
She showed leadership at her new workplace.
十分な準備があれば力を発揮できる。
With sufficient preparation you can perform well.