Whilst you cannot be reconsidered in the same session for a course you have already been rejected for, you may be considered for up to two additional choices (subject to a new administrative fee). You can submit a new personal statement to the graduate admissions office. Use the online How Do I forms to do this.
If you do wish to be considered again for the same choices, you will have to have your application reinstated in the next academic session. To request this use the online request form.