Gather the school ID of each school you plan to withdraw an application from if one already had been assigned to you. Some schools may need that ID in order to withdraw your application accurately.
Visit the admissions website of the school where you would like to withdraw the application and see if there is any protocol listed for the withdrawal. Some schools may have a form you can use for application withdrawal on their websites, and others may request an email or letter.
Call the school's admissions office if no information is listed on withdrawing an application or if you just want to double-check the information listed on its website. Be prepared to give a reason for the withdrawal, such as medical or financial obligations.