Welcome to CD Freaks, krishn
As far as I can tell, you can use this card without connecting its molex power connector, as the majority of satellite PCI cards don’t even have a molex power conenctor on them. There is also no mention in the manual that this must be connected to the PSU. This is likely for if you get the optional Common Interface (separate add-on for CAMs and viewing cards), which would draw extra power.
The best way to find out is to connect it (e.g. borrow a molex power cable from a CD drive if necessary), set up the card, drivers, software, etc to ensure it’s functioning properly. Then power off the PC, disconnect this power cable, boot the PC and check if you can still tune in satellite channels. If the card still works, then it’s not needed in your setup.
If the card will not work without power supplied to this molex connector and you’re short on power cables, you can pick up a 2 in 1 molex splitter from most good PC hardware suppliers, to connect it.