Drummerboy

Hi I hope someone can help as I'm confused with the Embassy website and some conflicting information for certain things. I recieved a letter from the NVC in New Hampshire stating mine and my Fiancée's application had been sent to the US Embassy in London, I then recieved a letter from the Embassy in London, stating that they had recieved our approved petition and then gave me a website for applying for my visa. I went on this website and the first thing was to apply for my DS-160 online application I have done this and completed it and printed off the confirmation page like it stated, what happens next ?? Does the Embassy get notified electronically that I have completed this online application and then s3nd me out an appointment letter for making a booking for my medical examination or do I just ring the number myself anyway and make a booking ?? I just don't know if I'm supposed to wait for a letter through the post or something stating that I am ok to book the medical exam and when to book it or if I can just book it anytime from now.  Any help will be gratefully appreciated as I'm not sure wether to just go ahead and ring the number anyway given on embassy website to book medical exam. 

Kind Regards: