Ensure your model is exactly the HG8245W5-6T.
For most users, the safest way to update the firmware is through the device's built-in management tools rather than searching for external links, which may host incorrect or malicious files. hg8245w56t firmware link
Use your admin credentials (often found on the sticker at the back of the router). Ensure your model is exactly the HG8245W5-6T