The instructions on the HKN website say you don't need the script on both computers, although you can load one on each computer, and this might help when it comes to subroutines. You only need a script on the computer if you happen to be trying to control stuff directly from that computers input. The issue with multiple computer scripts will be that some things are reversed, such as who is the second pc, and who is not, so you'll have to keep track of that and make adjustments as necessary.

It would also help if your game was installed to the same location, otherwise you should adjust your script to have different launch commands for each PC depending on the installation path. I can't seen an easy way to make this decision so you can either duplicate the <COMMAND Launch> with the appropriate paths, or you have individual scripts for each computer and call the launch on the second PC as a subroutine, or finally, you could load it yourself on each computer, and in your script, give each WoW a different name.

You also need to update the script for little details like IP_ADDRESS_2 . You could potentially use a variable here, but you still need to set the value somewhere.

Once you load the script, hit Scroll Lock to turn on your hotkeys, then you should be pressing ALT+CTRL+L to load WoW, as per this element.
<Hotkey ScrollLockOn Alt Ctrl L>