Sophomore year is the time to start researching colleges and universities. Early in your senior year you will apply to colleges and universities that interest you, so you have one more year to decide what your educational direction will be after high school. Apply to NIU by November 15 of your senior year.
Remember that you're trying to find the best fit for your educational goals and your accommodation needs. For example, if you are accustomed to taking your exams with unlimited time, ask the college how it would work there. Sometime during your sophomore or junior year you may have to go through additional tests to document your disability. See Guidelines for Documentation.
Start your research by asking others what they know about different institutions, check their web sites, and ask anyone you know who has attended that school about it. Visit universities if you can. NIU has Open Houses throughout the year. Be sure you contact the college's admissions department in advance if you need accommodations for your campus visit.