HHR SS Performance Flash
 

When you Flash do you have to set the car in some service mode or connect some test connectors together or just place the Ignition to on / run but not start ?

Flash what exactly ?
Kind of depends on what you're referring to.

Installing Performance TrifectaTune to ECU

Well. That should all be covered by the Trifecta dealer you are using. I don't have Trifecta in mine, so I'm not familiar with their procedure.
Just follow the instructions that come with your tune purchase.

The instructions and support from Trifecta are great, and they will help you out with a simple phone call.

Just remember there are times when Vince is the proverbial "One Man Band".

Sadly we lost the Zen Master of the Trifecta Tune with the passing of CJ Krause, but everytime I nail the throttle on my HHR's, I remember my late friend with a smile.