ok .. here's the deal .. and NVQ is an ASSESSMENT of your competency to do the job ... so whoever gave you the NVQ must think you are capable, or potentially capable of completing the qualification.
It will be your employers responsibility to teach you what you need to know, or gain the experience in the areas that you will be assessed .. it's your NVQ assessors responsibility to seek evidence from yourself, your employer and your peers to show that you can do the job.
There are many types of evidence they will be looking for .. knowledge, where you answer questions or write statements, performance, where you are observed doing your job & others .. just remember your assessor is there to help you ... make the most of them & good luck.
PS .. you will already have evidence that will no doubt contribute to your NVQ ... !!!!