Believe most have already given the answer, but here goes. First, protect yourself from the sun, use a sunblock, if you are out in the sun a lot, go for an SPF of 50 or better, if occasionally perhaps and SPF 15. If you are out and sweating reapply the sunblock often. Make sure you drink plenty of water. At night wash and apply moisturizer.

Most importantly, protect yourself from the sun and your skin will improve, also drink plenty of water.