If your BD player is already on your network the menu of the player will have a place for you to update the player firmware.
You can't connect a BD player to a PC to do this. You can use a wired ethernet connection if you don't have WIFI.
If the player isn't internet capable you may be able to download a file, burn it to a disc, and "play' it. Check the owners manual and Sony website for firmware upgrades and how to do it.