I don't know what to do.

Jenny • twenty seven, married
So about two days ago as you all may know, I received my Pre-seed in the mail. We are planning on using it tonight but I don't know when to put it in before BD. Anyone know when the right time to put it in. I just don't want to be one of those people who say "Okay I'm going to put pre-seed in so your going to have to wait 10 minutes". Please someone help me.