Your next step is to file a defence. You have hopefully been using the intervening time to conduct your own research and look at other threads, so that you know what you will need to do at each stage of the process.
As you will have seen from the other threads on here, a defence is, in essence, a short series of statements where you respond to each of the allegations in turn. For those allegations you deny, you provide a brief reason why.
In your case one arm of your defence is likely to be that you deny that a parking event took place, the vehicle being there for the purpose of unloading, which is different from parking as supported by Jopson v Homeguard.
If you show us what you have so far we can suggest how this could be improved
