Here is what you need to do to apply for benefits online:

• Print and review the Adult Disability Checklist.
  • It will help you gather the information you need to complete the application.
• Complete the Disability Benefit Application.
• Complete the Medical Release Form

You can use the online application to apply for disability benefits if you:

• Are age 18 or older;
• Are not currently receiving benefits on your own Social Security record;
• Are unable to work because of a medical condition that is expected to last at least 12 months or result in death: and
• Have not been denied disability benefits in the last 60 days. If your application was recently denied for medical reasons, the Internet Appeal is a starting point to request a review of the medical determination we made.

Find more information here from SSA.