The simplest approach to style any React application is to use inline styles. You don't need to build a separate CSS if you style elements inline. When compared to styles in a CSS, styles applied directly to elements take precedence.
You can use attribute selectors if you only want to style one type of input: Only text fields will be selected if input[type=text] is used. Only password fields will be selected if input[type=password] is used. Only number fields will be selected if input[type=number] is used.
Make the input element invisible.
Style a button element according to your preferences.