app.js

import Amplify, {Auth} from 'aws-amplify';
import awsconfig from './aws-config';
Amplify.configure(awsconfig);
//once the amplify is configured you can use below call with onClick event of buttons or any other visual component to sign in.
//Example
<Button startIcon={<img alt="Sigin in With Google" src={logo} />} fullWidth variant="outlined" color="primary" onClick={() => Auth.federatedSignIn({provider: 'Google'})}>
   Sign in with Google
</Button>