Any reasonable answer to your question is contingent on a number of factors, incuding:
The level of severity of the autistic spectrum disorder; the composition of the class; the staffing resources available; the policy and procedures of the particular school and/or school district; your training in behavior management.
This is a matter you should take up with your supervisor.
I am teaching, just started, what approach should I take to an autistic child in an inclusive early childhood environment?
This is a very general question about a very large topic. Much depends on the level of severity of the autism, the precursors to the definace, etc.