Purchasing a paint job in the Elite Dangerous online store allows you to use it in-game via any star port station services.
When docked in your Diamondback Scout bring up the Starport Services Menu. Navigate to the Outfitting menu and select 'Paint Jobs'. Any paint jobs you have purchased will be available to be applied to your ship.
Paint jobs/decals are for use with the PC version of Elite Dangerous ONLY.
This paint job is for use with the Diamondback Scout ONLY.
It does NOT alter the performance parameters of your ship in any way. It is purely a cosmetic item.
If your ship is destroyed, you will be able to re-apply any of the applicable paint jobs you have bought to your new ship in the star ports.