Your bios is fairly old, but unless you haven;t come across any issue, you may not need to change it. Saying, that, Dell will have added/fixed a few things along the way to A22.
Each BIOS update will differ somewhat but generally it will instruct you how to insert a floppy disk to create a bootable BIOS disk, and then instruct you to shut down the computer and boot it up with the BIOS disk in the drive. This will cause the computer to boot from the floppy disk that will install the new BIOS update.
A would also consider upgrading your memory to a minimum of 2GB, will make your W7 experience a whole lot better.