There is no free version of the add-on, only pro. So, you have to buy it in order to get it. Then installation process is pretty easy and straightforward:
Upload the plugin's files to the
/wp-content/plugins/uni-cpo-custom-product-urlsdirectory, or just make sure the plugin's files are in this directory.
Activate the plugin through the
Pluginsscreen in WordPress
WooCommerce->Uni CPO Settingsscreen to configure the plugin
Please, proceed to General Settings section.