How use a postgres database as if it were native to Rails

I am new to the rails world and I need to use an existing database for a rails project, for example I have a "games" table that does not have the columns created_at and updated_at, if I add them in the postgres terminal, rails would recognize my tables as objects ("Game" for example)? or should I generate the model for each table in my database? what would be the correct way to fetch all tables like a objects and use them from the controllers?