Scripting is a big topic, I suggest you start by reading documentation:
https://www.construct.net/en/make-games/manuals/construct-3/scripting/overview
These are Rexrainbow's Firebase addons ported for C3.
https://github.com/erenertugrul/construct-plugins/tree/master/ported_plugins/plugins/rex_firebase_pack
Chadori's Construct Master Collection also has Firebase addons:
https://chadorixd.itch.io/construct-master-collection
How could I add it to my construct project ??