How to change style of number box in framework 7 keypad plugin?

I just imported plugin and use framework7-plugin-keypad properly in my f7 react app.

<input id="myKeypad.value" type="numpad"></input>

How can I change location, size and color of number box ?

I looked for cssClass parameter which says Additional CSS class name to be set on keypad modal, how can I use it ? how to use it for number box ?