Can you please explain the api for creating a bdd?

How can I create a bdd?

How do I define it?

How do I give parameter names so that I can later use it to model check a formula?

What is the meaning of bdd_ithvar and bdd_nithvar and the int parameter they receive?

I would be very happy if you can supply a simple example.

Thank you very much and happy new year,

Miriam