dikshagautam1995 what are you trying to integrate?
If you just want to share login, then it's easier to keep the apps separate and just focus on the authentication.
If you just want federated login, you can use the Passport extension and expose an OAuth2 compatible endpoint from your separate app.
Implementing global login or single sign on is more complex, you could take a look at how the Wordpress/PHP SSO package works https://discuss.flarum.org/d/21666-php-and-wordpress-single-sign-on-sso-with-optional-jwt-addon
Integrating the two apps features together will probably be very complicated because the apps use different frontend framework and likely different backend frameworks as well.
If you need your app to be tightly integrated with Flarum social features, you could develop your app using Flarum as its framework.
