You need to have the 6 digit reference to log in, without it you won't be able to MMB (manage my booking).
Ring Virgin Holidays and ask them for it, explain it's the 6 digit code for use on the Virgin Atlantic site to enable you to MMB.
How to find your booking reference
How to find your booking reference number
A booking reference is a unique code specific to an individual reservation. It is also known as a Record/Booking Locator (or RecLoc), PNR Code, confirmation number or reference number. It can be found on your tickets, confirmation invoice or travel documentation.
Virgin Atlantic's booking reference is a six digit alphanumeric combination. E-tickets issued by Virgin Atlantic list this as a 'Booking Reference', which can be found on the e-ticket receipt under 'Ticket numbers & Endorsements'. The number starts with 932 and is 13 digits long. Tickets issued by Virgin Atlantic will contain this code in the PNR Code box near the centre of the ticket.
When checking in online: If you have used a middle name(s) when making your booking, you will need to add these to your first name in order to retrieve your booking.
For example, John Robert Smith would be entered as:
First Name(s): JohnRobert
Surname: Smith
We also accept booking reference numbers issued by most travel agents. These appear as a six digit alphanumeric combination usually listed in your travel documentation, or available from your travel agent upon request.
If you have purchased any holiday from Virgin Holidays, the reference can be found under "Airline Booking Reference". This can be found at the top of your holiday invoice.
If you cannot locate your reference or are having difficulty, please contact our call centre on 0844 209 7310.
If you get it now, you will be able to log in and see all sorts of info but the seat map will be unavailable. Might be an idea to get it and enter all the required info (passport etc).