I don't know what to do at university, how should I structure my personal statement.

It's okay not to know what exactly you want to do at university; there are various resources that can help guide you and allow you to make a decision. First thing is to think about, start to identify what you enjoy and then what you are good at. These two things will provide a very good foundation as to what paths to take. Make use of the people around you, speak to your teachers, your parents, your friends. Go online, there are so many resources about varying career; for example 'Tomorrow's Engineers'. This is a platform that aims to explain what engineering is to prospective student; what it entails; the different disciplines and how to become an engineer. A personal statement is really about showing your interest and like was mentioned earlier your interest lies in what you enjoy and what you're good it and thats where you can start to structure your personal statement.