In order to receive support services, you will need to have current documentation of your disability. Typically, documentation needs to be no more than three years old. It needs to be comprehensive and establish that you have "a physical or mental impairment that substantially limits one or more major life activities." This is the Americans with Disabilities Act definition of a disability. Ideally, you should see if your high school can conduct a comprehensive evaluation during your senior year.
UMKC uses nationally recognized guidelines for documenting disabilities. Follow these links to see what your documentation should include: