Letrozole 2.5mg

Wondering if anyone can help..I am just starting my first round of drugs tomorrow and the doctor hasn't really explained it properly to me..this is what I have been given and what it says on the box.. do I still keep taking the norethisterone even after I start bleeding or do I stop and do I keep taking the letrozole for the 12 days straight or something else.. just looking for a bit of advice or help as I can't get a hold of any doctors until Tuesday.. (it's Sunday today ) thanks for any help