This file contains the materials and models of the cube and companion cube
as well and check the Description for the tutorial
First you make a shortcut of the vpk from the portal 2 bin and then you drag the file to the shortcut and it makes a vpk.Second you have to copy the file and paste it in the portal 2 bin and do the same thing and when you've done that it would appear like this ( pak01dir ) change that into ( pak01_dir ) and run the game and enjoy :)
you ported the dx_level 81 version.