MeMetr look bro, im gonna explain this in the simplest way possible.
step 1: for any custom camo, download the files, like for example here on this post you can download the files here
click on that link
step 2: after clicking on that link, click the download button

step 3: wait for it to finish
step 4: open your downloads folder by clicking on this icon in file explorer

step 5: unzip the file

step 6: double click on this folder to open it

step 7: you will see these 3 .iwi files, select them all and copy them using ctrl + c
step 8: search for %localappdata% in windows search and open it
step 9: look for a folder called "Plutonium"

step 10: open the storage folder

step 11: open the t6 folder

step 12: open the images folder, if it doesnt exist, create it 
step 13: move or paste your iwi files here

pls man you cant possibly fuck this up too 