Help w/advice for my kids

NEED ADVICE ON APPLYING FOR SSI FOR MY CHILDEN. What's best for them? Both my children have been dx: with HS my daughter has suffered the worst. She endured years of pain, depression and emotional stress thru her early teens with this undiagnosed condition. My son was recently diagnosed too. seeking advice on appling for SSI for my children to help provide fir their healthcare needs and pay for their rx medication injection. I am a single parent currently on SSDI.