Text Messages - System Messages - Checkbox during checkout?

Hi,
Question 1: Do I have to do something to turn on this checkbox during checkout?

See This Image

Question 2: (possibly related) If my contact record has my mobile # and SMS Permission: Opt In, do I automatically get ship notices by text or I check that checkbox each time? (said differently: Do I automatcially get system text messages if I’m completely opted in for SMS? )