Paid add-ons for FW Rental for WooCommerce are delivered inside a pack — an ordinary WordPress plugin that you download from your client section on fastw3b.com. Install it the same way you would install any plugin: go to Plugins > Add New > Upload Plugin, select the downloaded file, and click Install Now. Once you activate the pack, its add-ons register themselves with FW Rental automatically.
FW Rental for WooCommerce never downloads or installs anything on its own. All installation happens through the standard WordPress plugin mechanism, which is why there is no Install button anywhere inside the plugin itself.
A lapsed subscription is an ordinary situation, not an emergency:
Renewing your subscription restores access to updates and support, and because your configuration was preserved throughout, everything picks up exactly where it left off.