Thank you for using Bitnami. In order to enable the Multi-Site support, we have this section in our documentation that explains how to achieve it, did you follow it?
In the Apache configuration steps, you needed to create a virtual host for Magento, so you can modify the Apache configuration to redirect all the incoming requests to non-www. sites to the www. ones. Before modifying the configuration, please create a backup of the current file in order to recover the configuration easily in case something is wrong
sudo cp -rp /opt/bitnami/apps/magento/conf/httpd-vhosts.conf /opt/bitnami/apps/magento/conf/httpd-vhosts.conf.back
You will need to modify the /opt/bitnami/apps/magento/conf/httpd-vhosts.conf file when following that documentation
After that, you'll need to restart the Apache service.
sudo /opt/bitnami/ctlscript.sh restart apache
Let us know if you have any questions about this process.