D-Link DCS-825L User Manual page 36

Step 4: Open a web browser and enter "http://IP_Address/eng/admin/tools_firmware.cgi"
in the address bar (where IP_Address is the IP address you made a note of in Step 3). eg:
http://192.168.20.56/eng/admin/tools_firmware.cgi
Step 5: If you do not already have the firmware file to use, follow the instructions on this
page to download the latest file from the D-Link Support Page. Then click the Browse...