Huawei provides firmware files on their official support site. However, downloading them usually requires a "Contract Account" or "Partner" status.
Open a browser and type 192.168.100.1 (the default Huawei ONT IP). Hg8247w5 Firmware Update
Most Internet Service Providers (ISPs) push updates automatically. If your firmware is outdated, contact your provider's technical support. They can "push" the latest version to your device remotely. Huawei provides firmware files on their official support