whats your price range? do you already have a cd player in your car with a sub pre out? how many watts rms (some lower end car audio companies rate all their stuff in peak power)
Don't wanna burst your bubble but you may find 1 10" lacking. I certainly did with a single 10" Kappa amply powered by MTX. See if you can get another 10" or trade for a 12.
You didn't give a whole lot of information, just the fact that you have a spare 10" woofer, own a '92-'97 Honda Prelude, and want this upgrade to be inexpensive. So, I'm going to make a lot of assumptions here. Please correct me if I go wrong anywhere.
First off, I'm assuming that the stereo equipment in your car is stock and you're not looking for "ghetto-bass". You'll still need dedicated amplification for the subwoofer. Head-unit power will not suffice. Get something good quality, but inexpensive. Go with a reputable manufacturer's entry level line of small bridgeable two-channel amps or single- channel amps. It will also need to be something that has high-level/speaker-level inputs.
Okay, now I'm assuming you're a "do it yourself'er". Naturally, you'll have tools and some very basic know-how of cars and woodworking. Go to Home Depot or someplace like it and get yourself some 3/4" MDF and build yourself an enclosure for that subwoofer. Try and get some specs from the speaker manufacturer. Most of them are pretty helpful. If your woodworking skills have something to be left desired, then you can buy a pre-fabricated enclosure. They have some good quality ones out there, but the only drawback would be the enclosure not being tuned for the woofer.
Now, install your amp and subwoofer. I'd tap-in to the front speaker outputs, so the sub fade with the front speakers. You can adjust the gain and/or volume level on the amp for the subwoofer to suit your taste.
no no no, not saying all 10" are the same... far from it. just saying a 10" sub with moderate power and moderate excursion is most likely all he is looking for.
get a better HU that can cross over the lows better. This will make a difference if you already have a decent amp running the sub. Don't run speaker line hookups from a factory, sounds terrible. Also you can make the sub face the inside of the car, just turn the box around. Thats the easiest way w/o making a new box. Also KEN, God bless you ED rocks and beats out everything for bang for buck. Really ED beats or is on par with any brand out there.