To continue: I'm assuming you have the KC-135R base file installed as per my earlier instructions. Also that you have downloaded the texture file named kc-135r_usaf_2004_61-0293.zip.
Extract kc-135r_usaf_2004_61-0293.zip & find a folder named texture.kc-135r_usaf_2004_61-0293. Paste this folder into the main folder of the KC-135R like so.

Now you need to edit Aircraft.cfg to add the new variation to it.
Find the file named
add to aircraft.txt in the texture download & open it in Notepad. Select all the text & copy it (Edit/Copy).
Open Aircraft.cfg in Notepad & paste (Edit/Paste) the text into it like this. (The copied text is in blue.)
[font=Courier][size=14]// Add your [fltsim.xx] sections here.
// Remember to start with 0 (zero).
// Copyright Historic Jetliners Group. No uploading of HJG materials to any website without prior
approval.
[fltsim.xx] // Change "xx" to next number in sequence starting from 0
title=HJG KC-135R USAF 22nd ARW 2004
sim=KC-135R
model=arr
panel=
sound=
texture=kc-135r_usaf_2004_61-0293
kb_checklists=
kb_reference=
visual_damage=1
description=HJG Boeing KC-135R
ui_manufacturer=Boeing
ui_type=KC-135R
ui_variation=USAF 22nd ARW (2004)
atc_id=61-0293
atc_airline=AIR FORCE
atc_flight_number=293
atc_heavy=0
atc_parking_codes=
atc_parking_types=MIL_CARGO,CARGO,RAMP[General]
performance=Length: 136.1 ft\nWing span: