Hi @Hong_Son,
Let me start off with some general information about Roon extensions and the Extension Manager.
Roon extensions can run on any device in your local network as long as it is on the same subnet as your Roon Core (otherwise the core cannot be discovered).
I created the Extension Manager to make installation of Roon extensions easier by taking away the hassle of using git, npm and other developer tools (but feel free to use them if you want to stay hardcore). This thread is about the old version of the Extension Manager for which I stopped support, the current 1.x version is supported via this thread. As mentioned by @Michael_Harris, the 1.x version requires a Linux system, but as that is what you have you might consider an upgrade. The first post of the linked thread, and this thread, have a link to the project Wiki.
If this is your goal then you don’t need the Extension Manager, as it is not included in the Extension Repository. To get this up and running you indeed have to use the git and npm tools as described in the readme of the Web Controller. As you probably have not installed the miemo version before, you should use the Installation instructions instead of the update instructions. Make sure that you have git and npm installed on your Linux system (e.g. on Ubuntu: sudo apt install git nodejs npm).