To install partner_address_street3, follow these steps:

1. Go to your project's directory:

$ cd ~/odoo-dev/my-odoo/src

2. Clone the 12.0 branch of the partner-contact project in the src/ directory:

$ git clone --branch 12.0  https://github.com/OCA/partner-contact.git src/partner-contact

3. Change the add-ons path to include that directory and update the add-ons list of your instance (refer to the Configuring the add-ons path and Updating the add-on modules list recipes of this chapter). The add-ons_path line of instance.cfg should look like this:

addons_path = ~/odoo-dev/my-odoo/src/odoo/odoo/addons, 
~/odoo-dev/my-odoo/src/odoo/addons, 
~/odoo-dev/my-odoo/src/, 
~/odoo-dev/local-addons

4. Install the partner_address_street3 add-on (if you don't know how to install the module, take a look at the previous recipe, Installing and upgrading local add-on modules).