Katherine,
There is only one company at the moment which will provide
car insurance for a learner driver and it is Collingwood. When you go to the Provisional Marmalade website, it will redirect you to Collingwood's site. As you probably know, insurance cover for learners is a risky business and therefore not many companies are willing to take the risk.
Your parents are probably already insured on their car, otherwise they would not be able to drive it. This means that you need to just find insurance cover for yourself and
Collingwood Learner Driver Insurance can give you just that so that you can practice in your parents car. The good thing about this type of insurance is that should you have any incidents while driving, you will be able to claim under your own policy and your parents no claims bonus would not be affected at all.