My son gets ssi where do i apply this to my taxes

[jerry2000]

You don't. If you child get true SSI - Supplemental Security Income, that is not reportable at all. If your child gets SSDI - Social Security Disability (or survivors) Income , that is income to the child, not to you. You do not enter it on your tax return. Look at Box 2 of the SSA-1099 and you should see the child’s SSN.
If that is the only income a child has, then the child does not have to file or report it either.
If the child has enough other income to be required to file, then the child reports the SS on the child's return.