So how do I know what universities want? Start by reading about the university, the course you want to study and the "entry profiles" as these will give you information about the type of student the university is looking for. Universities also want the truth so do not lie about your abilities and they want your writing so do not ask someone to write the personal statement for you. Some areas to cover include why you want to study this subject, what your future career plans are, what you do in your free time, what skills you have (academic and non_academic), what's interesting and/ or different about you.
To help you begin the writing phase, it is advantageous to split the writing task into three parts: the body, the conclusion, and the introduction. You can do so chronologically or follow your own sequence depending on your personal preference and style.