Received an I-797 in the mail. My wife's I130 was approved. What next?

I applied on behalf of my wife to receive an immigrant visa and was approved. We're both living in Shanghai and would like to relocate to the U.S. sometime in the next year. What do we do next? The I-797 states that we should wait to be contacted by the U.S. Consulate in our area, and that this could take up to 30 days. We're wondering what we'll be expected to do next (which forms to submit) as well as the timeline for receiving the interview. Does anyone out there know anything about this?