To install new add-ons in your database, follow these steps:

1. Find the names of the add-ons. This is the name of the directory containing the __manifest__.py file, without the leading path.
2. Stop the instance. If you are working on a production database, make a backup.
3. Run the following command:

$ odoo/odoo-bin -c instance.cfg -d dbname -i addon1,addon2 
 --stop-after-init

4. Restart the instance.

To update an already installed add-on module in your database, follow these steps:

1. Find the name of the add-on module to update; this is the name of the directory containing the __manifest__.py file, without the leading path.
2. Stop the instance. If you are working on a production database, make a backup.
3. Run the following command:

$ odoo/odoo-bin -c instance.cfg -d dbname -u addon1 
 --stop-after-init

4. Restart the instance.