Create few pages inside src/pages folder

// pages/Home.js
export default function Home() {
  return (
    <div>
      <h1 className="display-1 bg-primary text-light p-5">Home</h1>
    </div>
  );
}

Repeat the process for Login and Register

// App.js
import Home from "./pages/Home";
import Register from "./pages/Register";
import Login from "./pages/Login";

export default function App() {
  return (
    <>
      <Home />
    </>
  );
}

Install react router dom

npm i react-router-dom
// App.js
import Home from "./pages/Home";
import Register from "./pages/Register";
import Login from "./pages/Login";
import { BrowserRouter, Routes, Route } from "react-router-dom";

export default function App() {
  return (
    <BrowserRouter>
      <Routes>
        <Route path="/" element={<Home />} />
        <Route path="/register" element={<Register />} />
        <Route path="/login" element={<Login />} />
      </Routes>
    </BrowserRouter>
  );
}

Now you can visit different pages by typing in the url. For ex /login to view login page.