A "fine" is money that you have to pay because you did something wrong. For example, banks make you "pay a fine" if you try to take out more money than you actually have in your account.
When an organization makes someone pay a fine, we use the word "charge":
If you don't return them on time, the library will charge a fine.
You can say how much the fine is like this:
I was charged a $50 fine for filing after the deadline.