Booting failed: The selected file or folder is invalid or corrupted.

Newbie here!
Sorry if my question is easy or dumb!

Here are the steps I've taken:
- Download and install RCPS3
- Install Firmware
- Copy and paste files from my game's Bluray disc
- Click on "Open" icon in RCPS3 and select the folder containing game's files.

I get this error:
Booting failed: The selected file or folder is invalid or corrupted.

I tried reading the quickstart guide, but maybe I'm missing something.
Can you please help me?
A step-by-step instruction would be highly appreciated!