Where is the transmission dipstick for a 1990 Acura Integra LS located?

On the auto transmission the dipstick is located on the firewall side of the upper transmission mount

Manual transmissions do not have a dipstick. Unless you are familiar with your cars transmission explaining how to check the fluid levels would be pointless. Invest in a repair manual if you want to save some money on maintaining/repairing your car yourself. If you have an automatic then I don't know that answer. Standing at the front of the car with the hood open, look at where you battery is located along the left side... Just lower and to the right is where the dipstick is located. Factory dipstick should be of an upside down J shape and covered with a yellow vinal paint-like substance.