In this case, <App/> should be the component that manages the state so that <MyForm/> uses it as props.
Something like this:
const [firstName, setFirsName] = React.useState("Arun");
const [lastName, setLastName] = React.useState("Kumar");
// you'll need to define some event handlers to change the values
// the form component will use these
const handleSubmit = e => {
e.preventDefault();
// do whatever you need to do with the values
console.log("firstName", firstName);
console.log("lastName", lastName);
}
return (
<div>
<MyForm fname={firstName} lname={lastName} onSubmit={handleSubmit} />
</div>
);