Setting up VAT

Hello, New to Quickbooks and just setting up. I am trying to set up VAT when i get to the page where you enter details there is a drop down menu titled "when do you need to start calculating VAT from" I cannot get anything to drop down! I can fill in all the other stuff on the page though. I don't know if it makes any difference but we get Quickbooks through our accountant who is on holiday.

Many Thanks