How can I add WPS (pin) [for a WiFi capable CAMERA] to Time Capsuale WiFi

I suggest that you use the Add Wireless Clients feature in AirPort Utility.

Normally, this feature is used to add a wireless printer, but it will work with any wireless device.

Open Macintosh HD > Applications > Utilities > AirPort Utility

Select the Time Capsule and click Manual Setup

Click the Base Station tab at the very top of the screen

Click Add Wireless Clients

Sorry, I do not understand what you mean by "link" here. The camera simply becomes a wireless client of the AirPort router.