Your remote should have come with an IR receiver that is usb. On some TV tuner cards there is a port on the card itself that the IR blaster plugs into, but like mine and most others there is a port for the IR blaster on the USB IR receiver. The blaster is just a little IR Eye that you put in range of the Set Top Box so it can send signals to the box just like a remote does. I will see if I can find some pictures.
This is a complete kit with 2 IR Blasters. The square box is the IR receiver.