For 'In Year' applications received outside the normal admissions round, if places are available then children qualifying under the published criteria will be admitted.  If there are places available but more applicants than places then the published oversubscription criteria will be applied.

How do I apply for a place for my child at St Simon's? 

You should apply on-line at https://www.stockport.gov.uk/topic/nursery-and-school-admissions.