You need to follow all the instructions that were emailed you by the voucher site you booked with as well as print off the voucher you received and bring it to the course.  Please also ensure you book the correct name and email address of the person attending the course and remember, your booking is not complete until you have booked on formally via the link sent to you by the voucher site you purchased from, and printed your voucher to bring with you on the day!