first of all, find the addon file.
find a folder with the same number as the addon (for this one it's 3505181862)

open it with gmad, and get the hands textures.
edit them to your preferences, in any image redactor. save them, put in the separate folder.

now, create a folder in gmod "addons" folder. rename it to "white_knuckle_swep_climbing_and_parkour"
create inside the folder another one, call it "materials", inside materials create "whiteknuckle" folder, and put edited sprites inside.


custom hand sprites should appear in your game