How to use this library to convert AS3 to Haxe?

First thing first, I am a noob, never tried haxe before, first time ever and I just finished reading the entire Haxe manual and not really liking the language. [sorry]

But AS3 is dying and I kinda have no choice so here goes:

1:
I installed “haxe-3.4.7-win64.exe”

2:
I came across this:

and downloaded it.
Inside I saw three folders:
.github
src
test
Question: where do I copy and paste these to to install this into Haxe so that it can do its magic ?
I have a c:\HaxeToolkit folder but I have no idea where to paste it to.

Do what readme says.
So, you unpacked as3hx. Open cmd-console, navigate to that folder, run haxe --no-traces as3hx.hxml, then neko run.n /path/to/as3/input /path/to/hx/output.