Fallout: Equestria Book Project

I hope this doesn't sound like a dumb thing to ask but I was wondering in what form we will be getting the invoice an when are we supposed to pay? Invoices will be emailed out. From there you can view an online copy where you can pay via credit card. Everyone will probably have around a week to pay...

I hope this doesn't sound like a dumb thing to ask but I was wondering in what form we will be getting the invoice an when are we supposed to pay?