Once you have the generator running, unplug the fridge or whatever and plug it into the generator via an extension cord. You may get away with one of the orange long extension cords commonly sold at Home Depot, etc., but I would recommend using one of the heavy duty ones, even though they are more expensive, as they can carry more power safely without overheating. Make sure they are rated for outdoor use.

Place the generator (if portable) in an area where the exhaust will not get into the house. Carbon monoxide can and will kill.

A/C uses a lot of power, and usually requires 220/240 volts. Given you budget, you may not find a generator that can handle that load and the other things in the house.

Prioritize your needs. Our priority is the fridge and freezer (for obvious reasons and storage of insulin), sump pump (to keep basement dry) and only then "comfort" items such as computer (internet) and a small tv radio (when the power goes out here, the phone, internet and cable tv manage to stay on: YMMV). We use oil lamps and battery powered lanterns for light. No A/C. I can also get the gas furnace running off the generator if heat is required, but that is a bit complex to do.

Read and follow the makers instructions for storage. You want it to work then next time, and if not stored properly, there is a good chance it will not start easily or at all.