Magician, Sorcerer
Noun
まほうつかい
約束を守らないと、みんなから相手にされなくなるぞ。いいから、お前が先日会ったっていう、その魔法使いを連れてこいよ！
If you don’t keep your promises people won’t take you seriously, so bring the wizard you said you met the other day!
You know that 魔法 is "magic" so what about someone who uses magic? What are they called? How about a wizard, magician, or sorcerer?
The reading for 魔法 is what you learned with the kanji. The reading for 使い is the same as 使う.