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You didn't specify a year. You should be able to find a chrome fill plug with a large internal hex, located on or near your trans side cover on the right side of the bike, this is the fluid level check location as well as the fill location.
King of Cars - 2006 was released on: USA: 2006
King of Cars - 2006 King for a Day 1-5 was released on: USA: 2006
There's a filler plug with an Allen hole in it on the forward side of the transmission end cover on the right side of the bike. That filler plug has its own dipstick, which should be read with the bike upright (not leaning on the jiffy stand).
The transmission filler plug on all Twin Cam models is located on the transmission end cover (that's the oval-shaped cover on the right side of the bike where the clutch cable terminates) toward the front of the cover. It has a hex-shaped hole in it where the Allen wrench goes.
The King's Daughter - 2006 was released on: USA: 8 June 2006 (Chicago, Illinois)
Sneak King - 2006 VG was released on: USA: 2006 (Xbox version) USA: 2006 (Xbox360 version)
Walter King - 2006 was released on: USA: 3 May 2006 (Anthology Film Archives)
The Mummy Who Would Be King - 2006 TV was released on: USA: 3 January 2006
Return of the King - 2006 TV was released on: USA: 28 April 2006 (Norwood, Ohio)
King of Cars - 2006 Dunkarini 1-9 was released on: USA: 2006
bottom front left corner of the transmission pan. It's a 5/8" horizontally installed bolt that goes in from the front toward the rear.