If I understand correctly, your problem is only in the configuration of the react-router-dom.
index.jsx
import { render } from 'react-dom';
import Route from './route';
const rootEl = document.getElementById('app');
render(
<div>
<Route />
</div>,
rootEl);
Here you can import your route setup.
route.jsx
import React from 'react';
import { Switch, Route, Redirect } from 'react-router-dom';
import App from './components/App';
import Login from './components/login/Login';
import Signup from './components/signup/Signup';
export default () => (
<Switch>
<Route path="/signup" render={props => <Signup {...props} />} />
<Route path="/" render={props => <App {...props} />} />
<Route path="/login" render={props => <Login {...props} />} />
</Switch>
);
In this component I select the route for my App, Login or Signup component.
Within my App (or Signup, Login, and any other component you add on this route) I can have more routes, one that points to / form:
App.jsx
const App = () => (
<div>
<Switch>
<Route exact path="/" component={Dashboard} />
<Route path="/form" component={ComponentForm} />
</Switch>
</div>
And so you get to the component Form by your App component.
This link has a good tutorial on this.