Thank you for using Bitnami. From your message, I understand that you copied your app's files to the apache2/htdocs folder, is this right? Did you create a new folder inside that one? In order to know the status of your installation, we have a Support Tool that will gather relevant information for us. Could you please download and execute it on the machine where the stack is running by following the steps described in the guide below?
How to Run the Bitnami Support Tool
Please note that you need to paste the code outputted by the tool in your reply.
Apart from that, we have a guide in our documentation that explains how to deploy a custom PHP application on top of the LAMP stack, have you checked it?