It took them a little while (three weeks after I submitted AMCAS) to send it to me, so you should get it soon. It has to be returned within two weeks after you receive it and there are two/three essays.
1. "In your own words, explain your motivation for seeking a career in medicine."
2. "Please describe the geographical setting in which you think you would most like to practice following medical training. Include the following information if known: the region of the country, the name of the state, the region of the state and the name of the town and county."
3. "If applicable, indicate any special experiences, unusual factors, or other information not previously included in your AMCAS application or this supplement that you feel the admissions committee should consider when evaluating your application."
There you go. You can get a head start on those. It also asks for two personal references in addition to your pre-med committee/LORS. And they send a form requesting any summer grades. Okay, I think that's it. If you don't get it soon, I'd call.