WebSite-Watcher is a native Windows software.
If you want to use WebSite-Watcher on a Mac or Linux machine, you have to use a tool like CrossOver or a Virtual Machine.
If you don't already have a Virtual Machine that runs Windows, then a tool like CrossOver might be the best solution to run WebSite-Watcher.
CrossOver can be found at https://www.codeweavers.com
They also list WebSite-Watcher in their supported software list at https://www.codeweavers.com/compatibility/search?name=website-watcher