On the PCS site, under "manuals" are some programming guides and other information.
[Link: pcslighting.com]By all means, program by computer if you can. Manual programming at the switch is a pain in the rear.
I don't think you can use USB, but I'm not sure. I use serial. Since I use the same port for programming my Pronto, Ocelot, APC UPS, and PCS switches, I simply have an extention cable out of my serial port and plug in whichever one I am working with.
Deane