where do you add trans fluid on a 95 grand marquis

The same place that you check it at. But make sure you check the fluid level while the car is warmed up and running in park and also on a flat surface before adding any fluid. Also, I believe that car's transmission takes Mercon type trans. fluid not Dextron. It makes a difference, so make sure if you have to add fluid that it's the correct type. The parts store(Autozone, Advance, Oreilly's,etc) will know the correct one to use. You'll need a small funnel and pour fluid slowly down through the funnel into the dipstick tube located infront of the firewall (near the windshield) on passenger side of the rear portion of the engine. The transmission has a sealed system and you shouldn't need fluid unless it's leaking somewhere, usually around the pan gasket. F.Y.I., if you've got more than 70,000 miles on the car, I wouldn't advise changing the trans fluid, only add to it if needed. If you change the fluid after 70,000 miles and have never changed it before, expect a future needed rebuild to happen soon and those trannys aren't cheap to rebuild ($1500) The dirty fluid has alot of micro specs of dirt and metal shavings in it that are holding everything together, if you change the filter and fluid, that thicker fluid isn't there anymore and not keeping everything in sinc. I never change my trans fluid, just add if needed and have gone 250,000 miles without a rebuild.

MrBlueOval had some good advice however, ( Autozone, Advance, Oriellys) still have never gotten there information 100% correct. Case in point all have sold me wrong parts for my 94 MGM. Best bet even though the Big 3 aftermarket auto box's say not to with there current ads. Is still your local dealer.