How do you change the motor oil on a 2001 FLSTFI

In my first attempt to change my engine oil, I drained oil from bottom of my 2001 Fatboy, from the plug on the right side towards the front of the engine, just below the Twin Cam Cover and floor board (see attached picture) look at dark spot where plug is located, only approx 4 oz drained out, where is this from? How to I refill that oil?
P.S. I did find the right one mounted on the right side towards the rear of the engine, so oil is now changed.

Look at the bottom edge of the oil tank from the right side of the motorcycle. You'll see a large hose that goes towards the rear of the bike rather than the front towards the engine. It goes on down behind the transmission and emerges at the bottom of the frame behind the exhaust pipes. Look for a metal plug that is stuck in the end of the large hose.

On some year models, the hose goes down and connects to a "crossmember" at the bottom of the frame. Look underneath the crossmember and you'll see a plug. Screw the plug out to drain the oil.

Good Luck
Steve