How do I add a sandbox project / module ?

I am new to drupal and I am trying to add the kandy sandbox project to create video conferencing within the site. I installed and activated the shortcode module that is needed to work with the kandy sandbox module. When the install process i had learned did not work (it says "does not contain any "info.yml files"), I looked here online and found a step by step guide to work with git and install a sandbox project, though it was 4 years old so i don't know if it is still applicable.

I downloaded and configured git, then downloaded the kandy files on git, and I placed them in the modules section of the drupal site local code. According to the instructions, this should make the module appear as installed within the extend menu in drupal. This didn't happen for me. I don't know if I did something incorrect or if the instructions from 4 years ago are no longer correct.

Can you tell me how I can install the kandy sandbox / module?