Watching television on your computer can be as simple as plugging in a small USB stick device, intalling and setting up the software, choosing a channel to watch and then sitting back and enjoying.
Some things to bear in mind are:
Do you want to receive analogue or digital TV, or both? If you want digital, it's crucial to
check your level of coverage first - the antennae supplied with these products aren't particular powerful - you'll get much better results connecting directly to your normal roof aerial.