If you have installed the Bitnami MEAN Stack, you will have your Apache server running on port 80, and it serves the default page located at /opt/bitnami/apache2/htdocs.
If you want Apache to serve your application by default, you can do it following the steps below:
Start your application in your port, for instance, the port 3000.
Go to your /opt/bitnami/apache2/conf/bitnami/bitnami.conf and add the following lines within your default Virtual Host configuration. It should look like this:
ProxyPass / http://127.0.0.1:3000/
ProxyPassReverse / http://127.0.0.1:3000/
Now, you should be able to access your application at http://your-ip/