Making new modules available in an Odoo instance so they can be installed is something that newcomers to Odoo frequently find confusing. But it doesn't have to be so, so let's demystify it.
There are many Odoo modules available from the Internet. The apps.odoo.com website is a catalogue of modules that can be downloaded and installed in your system. The Odoo Community Association (OCA) coordinates community contributions and maintains quite a few module repositories on GitHub, at https://github.com/OCA/
To add a module to an Odoo installation we could just copy it into the
addons directory, alongside the official modules. In our case, the
addons directory is at
~/odoo-dev/odoo/addons/. This ...