This article tells you the time you'll need to have your picks finished by, and links to the racing schedule.

The deadline to select new drivers is always the night before qualifying. Please see the Auto Racing Schedule and Previews page for qualifying dates and deadlines for each race.

You will not be able to change (add/drop) the drivers on your team after the deadline for the upcoming race. The deadline for picking new drivers for the upcoming race is 2:00 a.m. PT on the night before the first day of qualifying. The deadline to change the activity status of your current drivers is five minutes before the scheduled start of each race.