I do not know how to install a tar.gz file
I read the answers to similar questions but it did not help me. My computer runs on Xubuntu, a derivative of Ubuntu. I am trying to install a package from this website : https://github.com/Zettelkasten-Team/Zettelkasten/releases/ I downloaded the source code (tar.gz) and extracted the archive to a folder, but I have no idea what to do next to install the programm that I am looking to use, or even where it is located inside the folder. I know how to handle basic commands on a terminal but I am lost when no detailed instructions are given.
Solution 1:
You cannot know how to install a .tar.gz package. A .tar.gz package is a compressed archive file, i.e., several files stored in a single .tar file, and compressed so they take less disk space.
To install software that is delivered in a .tar.gz package, you depend on the instructions provided by the software developper, in as far as the contents of the .tar.gz package does not give a clue. The contents could be a binarary file you can run directly, it could contain an installation script that installs binary files, or it could be source code that you need to compile and install yourself.
Take a look at the contents. Authors quite commonly provide instructions in a file called READMEor something else. If you need help installing one particular package, you may open a specific question for that package on this site. What I did here, is answering to the question that you currently asked.
In case of the application you link to, information on how to build the source code actually does not appear to be included in the archive. Some very sparse installation instructions are provided on the project's github page.
You may have better luck not compiling the application yourself, but instead selecting to download the .jar file, which should run on any supported java environment on Windows, Mac and Linux alike. I, for one, could fire up the interface with the command java -jar Zettelkasten-3.3.0.jar after downloading the .jar file on Ubuntu 21.04.