Preventing the production of melanin (dark pigment):
- Be a NEET and cover your windows to prevent both UVA and UVB from reaching you
- Go full Yohji Yamamoto. Cover your skin to protect it from the sun. Use a sunhat.
- Use a +50 SPF sunscreen on face/hands if you ever leave the house.
- Buy a +2% hydroquinone solution online and apply it as per directions.
For removing already existing pigment:
- Use salicylic acid/lactic acid/glycolic acid peels at somewhat low percentages.
- Start applying topical niacinamide products as per directions.
If you're excessively naturally melanin-augmented from birth, then you need to use a pulsed dye laser - repeatedly, everywhere.
In any case, see a derm.
D O N E
Ask for skin bleach in your local afro-store. Not even kidding. Same kinds of stores that carry chemical hair relaxers n shit. Popular thing among black women esp in the third world.