Right. As drarjun mentioned, first register with ecfmg if you are a foreign medical student or graduate. They'll give you an ECFMG/USMLE ID. Then you can start applying by going on ecfmg website, signing in and just following the instructions. They have online and paper applications. Once they confirm them with your college, you are ready to pick your dates etc.
Although, my suggestion is to first start studying for your exam and when you are nearly done with the prep or close to 70% complete, then you can pick your date because so many times people end up postponing their exam because they are not ready to take it.
Good luck.
