Myster62 Did you read the plugin document page and try any sample projects? (there are at least 5 of them). You should also check these tutorials:
https://www.scirra.com/tutorials/5015/getting-started-with-firebase
https://shatter-box.com/knowledgebase/firebase-sync-data-with-your-construct-2-game/
https://www.scirra.com/tutorials/9500/how-to-use-firebase-realtime-db-in-depth-tutorial
— There is a version for C3, but I don't know if it works or not:
https://github.com/rexrainbow/C3RexDoc/tree/master/repo
I understand, it would be necessary to do a test of the functions, thanks.