How do I define a workflow that is triggered automatically once a form is submitted in the form library?

I need to submit a form which triggers a workflow that goes through different stages. How do I start first, is there a simple procedure to make it happen?

please help me.

You need to have permissions to create workflows. Find the particular list that contains the form and go to List Settings > Workflow Settings. If I remember correctly SP gives you Three-State as well as a Disposition Approval workflow.

Have you tried SharePoint Designer? It allows you to set custom triggers as well as develop more advanced workflows.

See if this material helps.