From the manual...
When a software update is available, a yellow clock icon appears on the touchscreen’s status bar. Touch the clock icon to display the update window. You can then either:
• Schedule the update by setting the time you want the update to begin. Then touch Set For This Time. Once scheduled, the yellow clock icon on the touchscreen’s status bar becomes white. You can reschedule the update any time before it begins.
OR
• Touch Install Now to immediately start the
update process.