Copy the folder "Texture.CIRP to your SimObjects\Airplanes\Grumman_Goose_G21A folder(usual path is something like "C:\Program Files (x86)\Microsoft Games\Microsoft Flight Simulator X\SimObjects\Airplanes\Grumman_Goose_21A")

In your "Grumman_Goose_G21A" folder open "aircraft.cfg"
copy and paste the text below immediately after your last [fltsim.xx] text block (where xx is the last highest number) and then change the ".xx" to the nextest higher number (if the last fltsim block read [fltsim.10] change the .xx to read [fltsim.11]

you should be good to go! 

[fltsim.xx]
title=Grumman_Goose_G21A CIRP
sim=Grumman_Goose_G21A
model=
panel=A
sound=
texture=CIRP
kb_checklists=GrummanGooseG21A_check
kb_reference=GrummanGooseG21A_ref
atc_id=
ui_manufacturer="Grumman"
ui_type="Goose G21A"
ui_variation="CIRP"
ui_typerole="Twin Engine Prop"
ui_createdby="OZx HD Team"
description="S/N: B-49 Manufactured in March 1944 JRF-5 US Navy Surplus.\n \n re-registered as N3945C.\n re-registered N775G.\n re-registered C-CRGZ.\n Air Park Aviation Keyamawun Lodge 1982-1989.\n re-registered as N121GL.\n S.C. Johnson and Sons Racine, Wi 1990-1999.\n Charles Smith/ Rye, NH 1999-2007.\n N121GL Joel Thompson N. Carolina 2007\n Currently making it's way downunder to Cairns Australia"