Yup

Sorry my little joke. Okay copy the textures folder you wish to add into the aircraft in questions folder.
Next open the aircarft.cfg file in Notepad. Add something like the following (this is from FS9)
[fltsim.1]
title=de Havilland Comet Black Magic
sim=DeHavilland_Comet
model=
panel=
sound=
texture=1
kb_checklists=DeHavilland_Comet_check
kb_reference=DeHavilland_Comet_ref
atc_id=G-ACSP
atc_id_color=0xffffffff
ui_manufacturer=de Havilland
ui_type="DH-88 'Comet'"
ui_variation="Black Magic"
description="Built for speed and extended range, the twin-engine de Havilland DH-88 Comet "Grosvenor House" won the 11,000-mile MacRobertson race from England to Australia in 1934. Designed, built, and tested in just 9 months, the DH-88 Comet was the first British aircraft to include retractable gear, flaps, and variable-pitch propellers. Of the five DH-88 Comets built, only two--"Grosvenor House" and "Black Magic" (another MacRobertson race entrant)--survive."
Basically add one to the number from the texture above for the [fltsim.1] part and make sure the texture=1 has the correct name of the texture, in this case 1.