Transmission capacity on 02 heritage classic - 2002 Harley Davidson FLSTC - FLSTCI Heritage Classic

Looking under the bike up at the motor you'll see 2 drain plugs, 1 is motor and 1 is transmission.
Its easy to determine which is which because the transmission plug is vertical and the motor is horizontal.
Also you can drain the oil tank from the oil tank drain line which is plugged by a nipple on the frame. On the kickstand side of the bike, behind transmission.

Although I don't normally work on bike newer than 2000 models, I don't think they've changed the oil drain on the Softail models. Look at the bottom of the horse shoe type oil tank from the right hand side of the bike. You should see a line or hose going down somewhere behind the transmission instead to forward to the engine. Follow this line down to the lower part of the frame and you'll see a plug in the line. If you take this plug out, the oil in the tank will drain out. Capacity 3 quarts H-D Syn3 20W50 oil

Good Luck
Steve

3 quarts. H-D Syn3 20W50 or equil.

0.9mm and possibly about 3.5-4.0L w/ filter change

The oil drain us usually a hose with a plug in it that is held by a clip on the frame. It us usually on the right hand side of the bike just behind and underneath the transmission side cover. Loosen the clamp and pull the plug out. The oil will run out of the tank. Replace plug and add new oil to the tank.