You need to set your "document root" to the public folder inside your project.

Like the message says, you will need to set your document root inside Apache's httpd.conf

Code:

DocumentRoot "/opt/lampp/apache2/htdocs/YOURPROJECT/public"
<Directory "/opt/lampp/apache2/htdocs/YOURPROJECT/public">
...

or you will need to set the document root of your virtual host inside Apache's conf/extra/httpd-vhosts.conf

Code:

<VirtualHost *:80>
   DocumentRoot "YOURPROJECTROOT/public"
   ServerName yourproject.local
   ErrorLog "logs/yourproject-error_log"
   CustomLog "logs/yourproject-access_log" common
</VirtualHost>