You must first own a windmill to receive wind energy. Then make a device like a bicycle chain drive to transmit the wind force received by the windmill to the generator, and then install the generator. In this way, a small and simple generator is ready.
But it doesn't matter when it's windy. What if there’s no wind? Haha, the equipment to store electricity is quite expensive.
Added answer
I think it may not be easy for you to do it yourself. First of all, the design of the fan blades should always remain oriented towards the wind direction, and it should be reinforced. Additionally, the rotation of the fan blades drives the generator, so you must at least have a speed-increasing device in order to get sufficient power. Recently you need to configure a battery.