Have you seen the readme file on that page? Basically what dependencies and how to install and run its information are available on that page. There might be not a clear enough step-by-step installation process, but the information given should be good to start.
See this section:
Here I am again, It's been quite difficult to obtain all the necessary dependencies but I made it, the problem is that I still don't understand if MAIAN is a standalone software or it's part of another thing (maybe Python, I don't know).
Because the main installation file is apparently unlocatable, and calling commands via terminal doesn't lead to anything.
MAIAN itself is standalone software, it is just the code itself haven't been bundled into a standalone application.
If you manage to install all the required dependencies, you should be able to run MAIAN. Download or clone the repository above, on your terminal, open the "tool" folder up. And then run
python gui-maian.py.
You need to run the application directly on the code, so there is no installation file. Also, when you try to run it on the terminal, what does it show? any output from the terminal itself?