Contact SAM first and ask for the intake process.
As a disabled person, your autistic child has a legal right to financial support. However federal SSI has income limitations that you most likely will not meet. You must apply to SSI and be denied in order to be elligible to apply for a PA medical assistance card. Apply now, as it takes about a month to get an appointment. Once you are found ineligible for SSI, you become eligible for state assistance, which is the 'MA' Card.