In order for you to receive SSDI, you need to have accumulated enough work credits over the years. So in other words, it's like you are paying into disability. The longer you have worked the more money you may get if you are approved for disability... IF you are approved. SSI is different, it is for people who are disabled and poor but don't have much work experience. Either way you must apply the same way, by having your doctor records sent to social Security and them sending you a lot of paperwork to fill out. Almost everyone gets turned down the first time. You can appeal if you are turned down and if you are turned down again you can go to a third appeal called an administrative hearing. That is what I had to do. In my state there was a 20 month long wait for a hearing so all told, I waited almost 3 years for my approval. Some get approved faster. Those with mental disorders usually take the longest for approval according to my attorney. But if you cannot work it's worth it.