Sorry for the .7z file, .zip would make it 280 MB, and even .rar would be 250 MB. Uncompressed size is 895 MB.
1. Select the appropriate file by following the filetree.
2. Copy the .DDS texture file.
3. Overwrite the scope texture of whichever mod you have installed.
If you dont have a mod installed, I have no idea where the texture goes, im not much of a modder... somewhere in your gamedata folder I guess.
4. Overwrite the old file, but always keep a backup.