cd 1 is the first day of red flow.
I would call your Doctors office for clarification to make sure, they may want you to count the day that you started spotting as day one.
Your first day is considered the first FULL flow day. So after you get your first full day of your period then it would be on the 5th day. I took clomid for the first time this month as well and had to to take it from cycle day 5-9. Good luck to you!! :)