I have had medical examination for CSS with the same medical board. You have to visit the hospital given in the letter. They take blood samples, urine sample, x-ray of chest etc, and the physician examines you physically.. Eye sight, bones, height, weight, etc. Its pretty simple, nothing to be worried about. Won't take longer than 2 hours. For CSS, we had a board constituted who kept the tests with themselves, but here I think we would be given the reports, and would have to submit them at the time of our joining, along with character certificate and the undertaking..