Portable generators can pose a serious safety hazard if used improperly.

Observe the generator manufacturer's instructions for safe operation.
Plug individual appliances into the generator using heavy duty, outdoor rated cords with a wire gauge adequate for the appliance load.
Never plug the generator into a wall outlet.
If connecting to the house wiring is necessary to operate a well pump, sump pump, furnace or other hard-wired equipment, have a qualified electrician install a manual transfer switch to prevent backfeed into our lines. The switch protects our workers and the public from getting injured by your power supply, and it prevents damage to your generator, wiring and appliances when power is restored.
To prevent carbon monoxide poisoning, never use a generator indoors. Only operate a generator outdoors in a well-ventilated, dry area, away from air intakes to the home, and protected from direct exposure to rain and snow, preferably under a canopy, open shed, or carport.
Portable Generator Hook-up to House Wiring

A typical (1) portable generator connection transfers power through heavy duty cable plugged into a (2) power inlet box which acts as a weathertight connection to the (3) manual transfer switch that powers selected circuits of the (4) main distribution panel.

To install a portable generator you need to install a generator transfer switch like pictures below. With this type of panel you can switch some of your homes circuit off of the power grid and then power them from a local portable generator.