App.js

<Router>
      <div>
        <AppBar position="static" color="default">
          <Toolbar>
           <Typography variant="h6" color="inherit">
             <NavLink className="nav-link" to="/">Home</NavLink>
           </Typography>
           <NavLink className="nav-link" to="/new/">New Fundraiser</NavLink>
          </Toolbar>
         </AppBar>
        <Route path="/" exact component={Index} />
        <Route path="/new/" component={NewFundraiser} />
      </div>
</Router>