How do I activate the camera on my LG Ultrafine display when it is connected to my MacBook?

Hello CasWu,

Thank you for using Apple Support Communities!

I understand from your post that you would like to know how you can activate the camera on your LG Ultrafine display when it is connected to your MacBook Pro. Which model of the LG Ultrafine display do you have? If you have the LG UltraFine 5K Display, as linked below in the first link, then the LG website linked in the second link will provide you with the user manual for the 5K display which includes great information on how to use all it's features like the camera:

LG UltraFine 5K Display - Apple

Product Manuals & Documents| LG USA Support

If this is not the model you have, please let us know so we can further assist you.

Best Regards.