How does a PC sound card be able to detect 433 MHz signals?
How is it possible for a sound card to detect 433 MHz RF signals?

A PC sound card CANNOT detect much above 20KHz.  It most certainly cannot detect anything at 100s of MHz. 

whats the principle behind it?

A "receiver" is a device that detects the Radio Frequency signals and converts it into an audio signal that your sound card can detect.

on a PC sound card hardware, how do I figure out which points is the Vcc, GND and data input?

You linked to a USB audio "card". The gadget uses standard USB for power, ground, and serial data in both directions. How USB works is well documented and you should have no problem learning about USB.