Unscrew the tail cap, remove the battery holder and insert the batteries in the correct polarity as indicated on the battery holder. Re-insert the battery holder in the flashlight and replace the tail cap. Use the on/off switch to operate the light as needed. The yellow glasses improve visible contrast greatly, especially in low light or at night. additionally, they protect your eyes. dependant on light level conditions these glasses can be highly beneficial in both increased vision and eye protection. This is not a toy. Restrict its use from minor children. UV radiation can be harmful. Avoid shining the UV light directly into the eyes.