Does the car sub have any crossover network included? Or, is it meant to be driven from an external crossover? If so, what does the receiver have in the way of LFE crossover settings? You will require an external amplifier, I would guess, from the brief description you've provided. And, as a rule, car subs do not work well in the larger environment of a home. If you have no crossover, no amp and a sub poorly suited to your needs, I would suggest you save enough to buy a proper sub for your HT use.

As Jan stated, you will need an amplifier, a properly designed enclosure, and some way to adjust were the sub kicks in and the other speakers don't try to reproduce the low frequency signal.

Actually, some decent results have been obtained with some so-called 'car' subs.

It all boils down to the diver's Theil small parameters, ( http://www.thespeakerstore.com/glossary/understandingspecs.htm ) and designing and building an enclosure to match ( i.e. Box volume, sealed or portedbox, port length and diameter, etc.)
If you are interested in building a sub or buying a pre-made enclosure like ones available from Parts Express, the guys here are a V good resource for info: http://www.htguide.com/forum/forumdisplay.php4?f=6

These are a good 'bang for the buck' option, IMHO.
http://www.hsuresearch.com/products/stf-2.html