You can update your Wii using the built in update function of the console.
This is the safest and easiest way of doing it.
It is possible to manually update the console by downloading the required WAD files (use NUS Downloader to simulate a Wii System Update) and installing them with a WAD manager. This method is however not recommended unless you know what you are doing. It is NOT possible to change the region of the console to another region with this method.