You can either install all of the paints or specific ones for specific planes.

To install, place the folder texture.rustsempty in the super otter empty folder 
(normally C:/Program Files/Microsoft Games/Flight Simulator 9/Aircraft/Super Otter Empty)
Then, place the texture.rustsloaded into the Super Otter Loaded folder, and the texture.rustswheeled
into the Super otter Wheeled folder.

Next, add these lines to the Aircraft.cfg

FOR SUPER OTTER EMPTY:

[fltsim.4]
title=DHC-3 TTC Super Otter (Empty) Rusts Flying Service
sim=Super Otter Empty
model=
panel=
sound=
texture=rustsempty
kb_checklists=Super Otter Empty_check
kb_reference=Super Otter Empty_ref
atc_id=N2899J
ui_manufacturer=de Havilland
ui_type=DHC-3 TTC Super Otter Amphib. (Empty)
ui_variation=Rust's Flying Service
description=The DHC-3 TTC is a conversion from Texas Turbine Conversions (R). This Otter has received a more powerfull turbine to reduce the take-off distance. Other benefits are a larger operating range and a more important cargo payload. The interior is a more luxurius custom version.
atc_id_color=0000000000
visual_damage=0
atc_heavy=0
atc_airline=Rust's Flying Service
atc_flight_number=

FOR SUPER OTTER LOADED

[fltsim.4]
title=DHC-3 TTC Super Otter (Loaded) Rusts Flying Service
sim=Super Otter Loaded
model=
panel=
sound=
texture=rustsloaded
kb_checklists=Super Otter Loaded_check
kb_reference=Super Otter Loaded_ref
atc_id=N2899J
ui_manufacturer=de Havilland
ui_type=DHC-3 TTC Super Otter Amphib. (Loaded)
ui_variation=Rust's Flying Service
description=The DHC-3 TTC is a conversion from Texas Turbine Conversions (R). This Otter has received a more powerfull turbine to reduce the take-off distance. Other benefits are a larger operating range and a more important cargo payload. The interior is a more luxurius custom version.
atc_id_color=0000000000
visual_damage=0
atc_heavy=0
atc_airline=Rust's Flying Service
atc_flight_number=

FOR SUPER OTTER WHEELED


[fltsim.4]
title=DHC-3 TTC Super Otter (Wheelsed) Rusts Flying Service
sim=Super Otter Wheeled
model=
panel=
sound=
texture=rustswheeled
kb_checklists=Super Otter Wheeled_check
kb_reference=Super Otter Wheeled_ref
atc_id=N2899J
ui_manufacturer=de Havilland
ui_type=DHC-3 TTC Super Otter Wheeled
ui_variation=Rust's Flying Service
description=The DHC-3 TTC is a conversion from Texas Turbine Conversions (R). This Otter has received a more powerfull turbine to reduce the take-off distance. Other benefits are a larger operating range and a more important cargo payload. The interior is a more luxurius custom version.
atc_id_color=0000000000
visual_damage=0
atc_heavy=0
atc_airline=Rust's Flying Service
atc_flight_number=

Thats it!  Youre ready to fly