Are your hands darker than your face? This is because most of us when applying a sunscreen we mainly concentrate on our face ignoring our hands.
First step you need a sunscreen. Use a sunscreen with either SPF 30, 45, or 55. This will prevent further sun damage.
Then you need a skin lightening cream.
Use a chemical peel twice a week to help remove superficial layers of dead skin to help better penetrate your Skin Cream.