Yes, you can. If you do so, they become effective with the first pill. If you start them on another day, you should use a back up method of birth control for the first seven days.
If this is your first time taking birth control, you have several options on when to start:
1. Take the first active pill of the package during the first 24 hours of your menstrual...
I have taken the morning/day after pill 3 times and I've never experienced any spotting. I guess it is different for everyone though!! Sorry I can't help more...