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 let's get familiar with that.
There are many Odoo modules available on the internet. The Odoo app store at apps.odoo.com is a catalog of modules that can be downloaded and installed on your system. Another important resource is the Odoo Community Association (OCA) maintained modules, also available on GitHub at https://github.com/OCA/. The OCA is a non-profit organization created to coordinate community contributions, promoting software quality, development best practices, and open source values. You can learn more about the OCA at https://odoo-community.org/.
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/
. However, this is not a good idea...