Depends what your course is really Emma, and do you mean a personal statement as in an application? Try to briefly discuss what you've done in the past, jobs, educational successes, volunteer work etc, then move on to personal skills and attributes, with evidence to support these, and then finally why you feel you'd be successful in this new role.
I would advise you to go to thestudentroom.co.uk and go to the PS advisor section so you can get someone who is studying the same course as yours to look at it. If it's a Psychology one though I can look at it :)
From your question I think you might be filling in a UCAS form. If so, and you are at school/college, then surely you will have a tutor who will help you with it.
you should show your tutor at college if possible as they are experienced in how these should be written and can give you all the hints and tips you should need!