Modules for Magento 2 will usually have a README file in the module package. Follow the instructions from that README file to install the module.
Important
- Make sure to follow all steps in the correct order.
- Do not skip any step or CLI command!
- For a Composer installation, all path names must be 100% correct in the file composer.json
- When installing from a ZIP / TGZ package, the path to the directory which contains the package must usually be given, not the path to the package itself.
For more details about using Composer, please check this article.