How do I make checkboxes and buttons call a js function?

So I am working on a project for class and two things that my professor wants us to do.

User can enter 2 numbers in 2 text boxes and click a button. Include 4 radio buttons (Add, Subtract, Multiply, Divide) that will specify which operation should be performed. Include a button that calls a function that performs the calculation and displays the results.

and -

Button – when clicked, increments a number or decrements a number based on status of a checkbox. Use increment and decrement operators.

I am hoping someone can help me or at least point me in the right direction. I don't know how to make checkboxes, buttons and js functions work together.

Thank you in advance!