It is not true that people with darker skin tones are immune to skin cancer. People with darker skin do develop skin cancer, but less often than those with lighter skin.
Medical News Today
Link: https://www.medicalnewstoday.com/articles/325769
How is the sunscreen used?
The sunscreens must be used daily on the skin where it is open for sun exposure. According to American Skin Cancer Society Sunscreen needs to be reapplied at least every 2 hours to maintain protection. Sunscreen can wash off when you sweat or swim or when you dry off with a towel, so it might need to be reapplied more often. Some people may find they need to reapply sunscreen more often regardless of the activity they’re doing outside. Always be sure to read the label.
Even if you use a sunscreen with a very high SPF, this doesn’t mean you can stay out in the sun longer, use less sunscreen, or apply it less often. Again, always be sure to read the label.
Always follow the label directions for applying and re-applying sunscreen products. Most experts recommend applying sunscreen generously whether it’s your first time using it for the day or you’re re-applying it after a length of time.
When putting sunscreen on:
Pay close attention to your scalp (including hairline), face, ears, neck, arms, and any other areas not covered by clothing. Don’t forget your lips. Use lip balm with sunscreen when possible. When you wear insect repellent or makeup, put sunscreen on first. Set an alarm or timer on your watch or phone to remind you to re-apply sunscreen at least every 2 hours or more frequently if needed.
Ideally, sunscreen should be applied generously. You might see instructions saying to apply liberally or generously. Or you might see a recommended amount to use. It’s important to use enough to have full coverage of arms, legs, neck, face, and any other areas that are exposed to the sun.