I raced the new circuit on F1 Challenge (I've a modded Hungarian '07 version - don't ask), and I hate it. I can't believe that Suzuka was forsaken for that!
Well, something's gotta race there. Indy was unusual, and provided some decent races, but it was painful to see the cars going around that tight section. And no, I'm not keen on that antiquated circuit called Monaco either.
Drive into the pit lane, come to a halt in one of the boxes painted in front of any of the open garages (it's good etiqutte to stop at one of the last ones), and the crew will work on the car. Adjustments can be made beforehand by pressing F12, and changing your settings. Once the stop is complete, just accelerate away...
When you see the Yellow Flag warning pop up, be vigilant, be prepared to slow down. It may of course denote a hazard off the course, a hazard on the racing surface itself, or a hazard that wholly or partly blocks the racing surface. This informs the driver to prepare to stop, if necessary.