Installing this should be pretty simple. First off, choose the skin+HUD pack you want, then do the following:

For the "hvyweapon" folder:
-Extract to "C:\Program Files\Steam\steamapps\YOUR USERNAME\team fortress 2\tf\materials\models\player"

For the "HUD" folder:
-Extract to "C:\Program Files\Steam\steamapps\YOUR USERNAME\team fortress 2\tf\materials"

***Note: THE RED OPTIONAL SKIN ALSO INCLUDES A BLUE TEAM SKIN, SO DON'T GO AND MIX THE FOLDERS OR IT MIGHT SCREW UP!!!***