Hi,
Topical lightening creams are a good way to start. Some degree of lightening will be achieved if used appropriately over a period of 3-6 months.
If that fails to give you the desired results, consider pigment laser treatment as this is effective in removing sunspots. You may wish to read more about this option which has been well covered in other parts of this forum.
A face-to-face discussion with your preferred aesthetic doctor will help you select the best treatment option based on your response to previous treatment, expectations, tolerability for treatment downtime, and cost considerations.
Hope this helps!