Step 1: Download a model. This can be any model from the CS section or CS:CZ section.

Step 2: Examine the files. What are the files, if they say v_m4a1, do not change them or else for the gun you try to replace it will mess up.

Step 3: Locate your cstrike folder. Find where your cstrike folder is, this is one of the places you will need to find to use your new skins.

Step 4: Locate your models folder. Here is where the skins work. Place all .mdl files in the cstrike\models folder, and for all the players, in this case, a leet model put them in this directory, cstrike\models\player\leet\.

Step 5: Use your skin and enjoy it.

Warnings

Some skins from CS:CZ section will not work in CS 1.6 because it is made only for condition zero. If this happens, find the model it says, and delete the p and w model just in case, so it wont happen, the v model should work fine.

I Hope This Helps You.

An easy tutorial, by XISHNIK.