My ergonomic keyboard does not have a specific button for right clicking. Looks like the Windows key has been combined with the right-click button. But I don't know how click it so it works like right-click mouse button.
You can always use SHIFT + F10 to access context menus in Windows, even if your keyboard doesn't have a dedicated key or if the key doesn't work as expected. As noted by @jcrawfordor you could look for an Fn key, but that's unlikely on a desktop keyboard. Another option is to try ALT-GR + WIN to access the context menu function on your windows key.