Inside the player folder, you will see subfolders for each default character (e.g., arctic , gsg9 , leet , phoenix , sas , spetsnaz , urban , vip ). To replace a specific character, copy the downloaded .mdl file into its corresponding folder. Some skins will have their own specific folder names which must be pasted directly into the player folder.
Do you have a holy grail skin from 2007 that you can't find anymore? Let us know in the comments below (or on the subreddit). cs 1.6 girl skin
See a where you can still download these classic skins? Inside the player folder, you will see subfolders