You can install modules and add-ons from the admin panel of the application. To install a new module in Odoo, follow the next steps:
Log in to the Odoo administration panel and on the top menu bar, click “Apps”
In the Apps menu, you will see all odoo apps. Search for the plugin you want to install.
Click the “Install” button in the plugin you want to install. If it already installed you will see the plugin will appear as “Installed”