Software and firmware are actually two totally different things. Software describes a program that you're able to load on your PC to program your scanner which keeps you from having to do it my hand. Firmware is how the "brains" of your scanner is configured at the factory.
For the software, there are a couple of options. One is USAD, which is available off the Uniden website. The other, and the one that is generally recommended to everyone, it ARC246 from Butel (
www.butel.nl). The Butel programs are very user friendly and easy to use.
As for the firmware, if your scanner is new, then you shouldn't have to worry about upgrading your firmware. However, if you've had it a while, or got it used, you might consider downloading the firmware upgrades from the Uniden website. The firmware upgrade will fix known "bugs" the scanner has.
Good luck...