Good answeres but a little more info might help. Chances are the primary is the one you are after because it is harder too find and often overlooked. On the S it is indeed near the gass tank but for easy access pull the rear drivers side wheel and thar she blows. If you already have the replacement you know what it looks like but it actually sits in a little metal cup and it will be covered with crud so at first glance it looks different than the new one. There are three hold down "fingers" that appear to be spring holders. Not springs just holders. Pry them away enough so that the filter can be removed. Clean off as much dirt as possible and then remove the two spring hose clamps. Before you reinstall the new filter clean out the inside of the afore mentioned cup trust me if you don't you'll never get the filter to seat properly and the tabs won't bend back into place. One thing to bear in mind is to replace this filter before you need to otherwise you put undo stress on the fuel pump, and you don't want to have to replace that. If all goes well pat yourself on the back and then replace the pcv valve. It costs about $3 takes less then 5 min and is critical on this engine.
Tweety20 answered the question if your 89 Prelude is an Si. However, if your prelude is an S the filter is an inline device close to the firewall on the driver side. You will find a second filter (or I should say first) coming out of the gas tank on the driver side of the gas tank.
Well the answer is simple but will require a bit of searching for the components.The fuel filter can be located under the hood.It is on the passenger side of the firewall.It will be a black colored canister and it may leak so have something with you when you want to remove it.Furthermore if your steering wheel is on the left then it can be found on the driver side situated under the hood.The second filter is behind the rear left wheel.If you feel you still cannot access the filter and may do damage to the filter or yourself while removing it,I suggest you call a mechanic who knows how to handle the car expertly.