Download Autohotkey from: https://autohotkey.com/download/ahk-install.exe
Install it. If it asks, you want the Unicode version.
If you are running 32 bit windows, you want 32 bit AHK, if 64 bit windows, 64 bit AHK.
If you don't know if your windows is 32/64 bit open System Control panel or press windows key+pause/break key and look at the "system type" line.

Open notepad and paste/type your script.
You may want this at the beginning of the script to have it run in administrator mode:
if not a_IsAdmin
{
	Run *RunAs "%A_ScriptFullPath%"
	ExitApp
}

Save it wherever you want, but make sure the name ends with ".ahk" (w/o the quotes)
Also the save as type should be "All Files (*.*)" not "Text Documents (*.txt)"

Now double click your file and it will start (and possibly prompt you for administrator confirmation if you included that part.
There will be an icon (letter H on a green square) in your system tray (the area down by the clock in the lower right).
You can right click that to edit/reload/exit your script.
You can now use any hotkeys defined in your script.