Sorry but is there a more detailed guide?.
A little warning beforehand: if you are not into command line on Window$ and checking out errors, then maybe better to stick with the machine translation stuff...
0. Open up a command prompt (cmd, command in search box) and change dirs to your directory where you downloaded/cloned the code. (with cd .. etc, startpage it)
1. On Win you can run the .bat scripts. There is one .bat file. Type that in: MakeQSP
2. Choose the option to generate the qsp file
3. Replace any (!) QSP file in your game folder with that one.
4. If you don't use git: make sure to check updates to the translations and download it again.
But: if this is too off for you, I reckommend you stick with the machine translation. Because the dev decided to do everything on his own and lock the code up, I am rather sure there won't be new translations for the git repo (well, not from me anyway). If the dev is reading this (Hey!): post a reply.