Applying is simple. You can do it online. Qualifying and becoming entitled - not so simple.

The previous poster explained work credits. If you have ever held any job in your life, you should file an SSDI claim AND SSI requires that if you could get SSDI, you have to.

Since you became disabled before age 22, you may be able to qualify on a parent IF the parent is deceased or entitled to retirement or disability. It is likely that someday your parents will be on retirement Social Security or will predecease you so even if you don't qualify on their earnings today, you may some day, as long as you remain unmarried (with a couple exceptions).

You should read about SSI work incentives, especially a Plan for Acheiving Self Support, PASS. A PASS allows for an exclusion of other income when you are pursuing a work goal. It would involve getting some type of job and then spending the money from the job on the education/training/items you need in order to get a career that you are capable of doing.

You need to also read about Impairement Related Work Expenses (IRWE) and SSI eligibility under section 1619a and 1619b which allows you to keep working but still being considered an SSI recipient as long as you meet all the other qualifications including limited resources and deeming of income from a spouse.

If you can manage to earn $5000-$6000 year for five years in a ten year period, you may get enough credits to eventually qualify for SSDI. You don't say how old you are, but in the long run, even if you get minimal SSDI on your own earnings, there are other benefits like Medicare that is in addition to Medicaid AND fewer restrictions on marriage than SSI or benefits from a parent's earnings. You are somewhat different from other SSI/SSDI benefits because your disabling condition is congenital and you cannot be cured or have medical improvement (unless there is some new procedure I am unaware of).

You can read all about work incentives at www.socialsecurity.gov in the Red Book.