What is the Philips HUE PIN?

I enabled the Philips HUE addon and it correctly identified my hub (recognize the number) but there is no information about where to get the PIN from.

What is interesting as that after I pushed the hue-link button, as seen in the logs, the gateway was able to discover my devices. Still, even after that, when I go to add new thing, the philips-due is still there to be added but I cannot add it due to the require PIN.

As a personal note regarding the UI in general, I find it very confusing and the lack of links makes unfriendly.

See: How to configure NetAtmo Thermostat to Mozilla IoT Gateway?

What do you find confusing? What would help?