Hi medococo,
I noticed you have recently attracted everybody's attention on this forum - but for all the wrong reasons (as nuisance). Anyway, I have the patience to tell you that: As a standard procedure your second package will have all the information on what to do or where to go. However, to quence your curiosity- medical examination/report from US Embassy-designated clinics are only accepted and in a prescribed forms only. Not medical from any good or very famous clinic will do. Usually, 2nd package will list the address of their designated-clicnics/doctors. If KCC does not include the required medical forms in your second package (I notice they usually omit this - possibly to save on postage), then you will have to ask and collect those from local Embassy.
You will need to bring to your doctor only your original passport, a US passport size photo, and medical examination fees (which depend on doctors).
Usually, amongst other things, doctor will test urine, blood, eye-sight, height, weight, blood pressure, chest X-ray etc. etc. Critical items they tests are whether you are infected with HIV (resulting outright disqualification), sexually transmitted diseasees (syphilies, etc.) or Tuberculosis (the later two and any other disease do not result outright disqualification). They will check your vaccination records (if you have any) and ask about the related disease history and decide which additional vaccinations you might need. For example if you never had vaccination for Chicken pox and you were never infected with chicken pox, they will have to give you 2 shots for it (in 4-6 week's interval. But the 2nd shot can be after your interview). But if you were not vaccinated for a particular disease but you once had it, then you will not require any vaccination for that (because once you are infected and recover, your body automatically develops required antibody for it).
If you want to expedite your medical (which is usually not required) you can email your local US Embassy to send you their list of designated clinics/doctors and then directly talk to one of the clinic even before you get the 2nd package.
Thank you.
-dreamer