Make sure all equipment is clean, dry, and sterilized.
To sterilize the jar keep it under sunlight for 2 hours. Or you can microwave it.
If you buy chopped mangoes directly from the shopkeeper then clean the mango pieces with a dry cloth.
Remove the skin of mango seed if you want.
Throughout a year whenever you feel oil is totally absorbed by pickle then heat some oil and when cool down, pour on top of the pickle.
This will help your pickle from fungus and your pickle will not be spoiled.
Store it at room temperature in airtight pickle or glass jar.