How to add Reflection + Shadow to a 3D Box in Photoshop?

I used a 3D Box Generator for Photoshop, and was able to create some boxes with it. These boxes were shaped in the form of Software Boxes, while I require Customized Dimensions Boxes, which currently I'm trying to create with Protomissume Software.

This software creates a box with no Reflection, and I disabled shadows in it, cause it doesn't allow transparency while saving to png. It allows custom dimensions, rotation, etc settings, but doesn't save transparency or reflections.

Here's the difference in output from both the above mentioned apps.. I'm trying to get the reflection + shadow in the 3D box Generator to the Protomissume generated image.

My question: How can I create similar Reflection & Shadow in Photoshop?

Images: 3D Box Generator

Protomissume Box Shot

Thanks for any help.