Yes, I know my social security number.
Great, you can mail your documents if you include your social security number on a separate sheet of paper and as long as you don't write anything on the original documentation.
I also need information regarding the child disability benefits. Can you tell me in detail the steps on how to apply for these benefits?
Gladly. First you should review the Child Disability Starter Kit. This kit answers common questions about applying for Supplemental Security Income (SSI) benefits for children.