BTC, this legislation relates to freedom of access and non-discrimination in employment for people with recognized disabilities. It would mean that if you can perform the job with reasonable accommodations (eg., freedom to leave your work space and visit the bathroom when needed), you could not be denied the job or fired because of your disability.
A common misconception is that if you're covered under the ADA act, you have to be hired or can't be fired or the employer has to do whatever is necessary to enable you to do the job. A blind person, for instance, would not be able to get a job that required driving a car and then demand a driver to transport them (although if they could perform the job duties using public transportation, they would be protected.) It also doesn't protect people from being terminated because of excessive absences.
When you speak of applying, I think you're speaking of Social Security Disability. This is a completely separate process, which provides benefits to people whose disabilities prevent them from working. In order to initiate that process, contact your local Social Security office or go to http://www.ssa.gov/ and click on the disability link.