Here's long write up I wrote awhile back on the basics of using nitrous:
http://temp.corvetteforum.net/c4/vader86/nitrous.html
Check that out sometime when you are bored. Keep in mind that I wrote that with the V8 small block in my corvette in mind, so some of it might not be 100% applicable to the turbo 6.
Normally, you use a toggle style switch to arm the system, and then a window switch to engage the system at a certain RPM. With my vette, there are several parameters that must be met in order for the nitrous system to activate, here's a short run down:
The system must be armed
The engine must be at WOT
The fuel pressure must be above 47 PSI
The RPM's must be between 2700 and 5800
If any of the conditions are not met, the system will not engage. This allows me to do my burnout, arm the system, stage, launch, and when the tach hits 2700 the juice comes on.
Start small, and monitor everything as best you can. If anything doesn't feel right, immediately get out of the throttle. N20 is even less forgiving that the turbo when it comes to mistakes in the tune.
Good luck!