Thanks for writing to us.
There could be many causes for pigmentation over face and hence the treatment protocol may vary according to underlying cause. You may follow these general recommendations to help with your concern
1) use a Glycolic acid
based face wash like melawash. Keep it over face for two to three minutes then wash off. Little bit dryness is expected
2) use a sunscreen with SPF 30 or above, even if staying indoors
3) take vitamin c, beta carotene
and antioxidant supplements
4) apply hydroquinone
4 percent cream over dark spot. Withhold use if redness or irritation occurs.
These recommendations might help you out but I would still suggest to meet a dermatologist
and ascertain cause of pigmentation. If topical creams alone do not help, chemical peels
and lasers can be done to reduce pigmentation.