For generators you have two choices.
1. Get a gas generator at Home Depot and run extension cords from it to your critical appliances, e.g., refrigerator and well pump, etc.
2. Get a generator that integrates into your electrical panel. Most of these will still not power the entire house, only critical circuits that are moved to the switchover box. In the event of a failure the main is switched to the generator and disconnected from the main. Once main power is restored the generator is disconnected and the main is restored.
The first is cheap, the second not so much. The first doesn't require professional installation. The second does. I've wired many homes but the generator crossover switch is something I'd prefer to leave to a licensed pro.
A google search yielded this:
https://www.instructables.com/id/Eas...-Home-Hook-Up/
claims it's code compliant, and the interlock would prevent feedback when on the main, but I'd want to be absolutely sure that your local codes allow it. Secondly, most portable generators only are good for about 30A, so running a whole house that has a 200A main is unlikely...