The pcIII is a fuel and timing manipulation unit. It will +/- fuel and timing from the factory ECU.
To make adjustments to it, you'll have to connect it to a laptop and use the PC software to edit it's values.
Say if you installed an aftermarket exhaust, did the air box mod and added a 40 shot of NOS. You could then take your bike to a dyno tuning shop and have them tune the bike for the changes you've just made.
The only way to know what changes to make to a PC is to collect data from a dyno, data logger or the SOP (seat of pants) for more experienced users.
So really the question is, what mods are done to the bike?
And welcome to the board!