I'm not familiar with that specific board, but generally for a 486 you don't have any flash tools that you can run from the command line as you do on more modern computers.

Some 486 boards have UV-erasable EPROM chips (these have a little window covered by a label), which means that you need to erase the chip using UV light and write the new BIOS with a ROM programmer (or just write the new BIOS to another chip that is compatible with the one that came with the board).

Another possibility is that the board uses an EEPROM/Flash chip (seems to be the case based on the pictures I found for your board). In this case you can erase and rewrite the BIOS using a programmer.

So, unless there actually is a tool that allows you to reflash the BIOS, you will probably need a programmer (or someone to do it for you).

There's also the "hotlfash" trick, but I won't get into that since you said you don't want to screw things up 😁

The first thing I would do is to find out what kind (manufacturer + model) of ROM chip you have on your board and then try to find an updated BIOS on the web or someone with that board who can dump it. Then you can move on to the flashing.

Those Eproms cant be flashed, they need to be programmed with a eprom programmer.. If you work on these boards an USB Eprom programmer from ebay is highly recommended.