This little guide will show you how to install mods for HL2*.
1. Follow: `C:\Program Files (x86)\Steam\steamapps\common\Half-Life 2\hl2`
2. In the hl2 folder, create a new folder called "custom" without the quotation marks.
3. Inside of the custom folder, create another folder, it can be named anything you want(I call the folder my_custom_stuff).
4. Extract any mods you've installed into the folder.
5. Launch the game and enjoy your mod(s). :)
MP5 skin: http://hl2.gamebanana.com/skins/44055
92FS skin: http://hl2.gamebanana.com/skins/43535
*This will also work with any Source game on Steampipe i.e. Counter-Strike: Source and Team Fortress 2.