im all confused on how to write the Java App or where to put it and I'm all clueless.
Moved to the API forum.
The Drop-ins for web are JavaScript components, so you would integrate them on the front-end of your site using JavaScript (not on the back-end, e.g., using Java, if that's what you're referring to).
Have you read the documentation for the Drop-ins yet? What do you have so far and where are you stuck?