Steps for preparation

Buy fresh peanuts from the market, you can buy a small paint bucket depending on how much oil you'd be needing, 3 cups of groundnut should give you about 1 cup of oil.
This is the most time consuming part unless you bought the groundnut that has already been shelled and cleaned up, you'll have to break the hard shells yourself and bring out the groundnut. Then remove the back, to easily do this you can fry the groundnut for like 5 minutes or wash them in cold water then warm water.
Put the peeled and washed groundnut in a clean bowl, then pour warm water on it. Allow the groundnut to soak in warm water for 10-15 minutes, so that the peanuts get little soft.
Drain the water, then take the groundnut to a local mill to blend, let them preheat the machine before pouring the groundnut. But if you have a blender, blend the groundnut until it becomes smooth like butter. To make it less difficult to blend, add 1 or 2 tablespoons of warm water but not too much water so it doesn't make it watery.
Pour the peanut paste into an air-tight container and cover the lid tightly. Leave the container inside the refrigerator for at least 24 hours. Do NOT disturb the container for rest of the time, after 24 hours or more, the oil have risen to the top of the container.
After the oil has risen to the top, you have to separate the oil from the paste, strain the oil into a separate bowl using a colander. Keep straining the paste until the paste is dry.
Strain the oil until it's completely clean, then pour it into a clean jar or bottle. Close the lid tightly and keep.