There are good reasons to switch to ZUI, but firmware upgrades is not one of them. HA supports the same functionality just fine.
Reading the add-on documentation would help (available as a tab on the add-on page), as it has step-by-step instructions on installing the integration, including the URL to use: app-zwave-js-ui/zwave-js-ui/DOCS.md at d130b3b97a5e46bc3769b6a16b12c5dca1b3a674 · hassio-addons/app-zwave-js-ui · GitHub
Or here’s a full guide to switch add-ons: