Think of the Garage pick as your bench.
You must select your Garage driver at least five minutes before the official start time of the Race, but you can substitute your Garage driver for a driver in the starting roster an unlimited number of times, if desired, until the start of the final stage while the Race is in progress.
The combined race points of the drivers that finish the Race in the Team’s five active starting roster slots will count toward the Team’s final score for that week.