The word ハンドル is often used in set expressions like:
ハンドル is a transliteration of the English word, “handle,” but in the above examples it is used as a “steering wheel”.
ハンドルをにぎる means to “take the driver’s seat”
ハンドルをきる means to "turn a steering wheel."
These days the word ステアリングホイール is also used, but still many people call it ハンドル.