Depending on how much you have to program, you can do it by hand or use software on your PC. If you use your PC, you'll need a cable to connect the scanner to it. There are 2 versions of cables that work with the PRO-97: a COM port version and a USB version. The COM versions are hard to find but used to cost ~$10. Radio Shack sells the 20-047 USB version cable for ~$35.
I use WIN97 (www.starrsoft.com) to program my PRO-97s (and PSR-300). There are other programs as well, plus a lot of information here. If you are new to things like "trunked radio systems", "talkgroups", and "alpha tags"; part of the difficulty in learning is the EXTREMELY POOR manual that RadioShack provides with the scanner. There is an online "easier to read" version that you should check out.
BTW, a lot of people ask how to use WIN97. Once you understand how the PRO-97 works, the software is really easy. You'll need to understand the scanner just to operate it anyway.