To commit something firmly to memory; to memorize or master so that it is retained.
新しい単語はノートに書いて覚えこむといい。
It's good to write new words in a notebook to memorize them.
彼女は舞台の台詞をすべて覚え込んだ。
She memorized all the lines for the play.
試験のために重要な公式を覚え込んだ。
He memorized the important formulas for the exam.