USMLE 2019 regustration basic requirement is to get ECFMG certufication. for that you have to fill a few queries on the USMLE application form 2019 for ECFMG certification. The steps are as follows:

(1) Identity confirmation

(2) Contact information

(3) Proof of having graduated or enrolled in a medical school listed in World Directory of Medical Schools.

You can apply for USMLE registration 2019 once you  have received the ECFMG certification. International aspirants are required to apply for USMLE 2019 through the IWA.  Candidates can register for USMLE 2019 registration for Step 1 and Step 2 (CK and CS) through ECFMG.

for more details: https://studyabroad.careers360.com/articles/usmle-application-form

https://studyabroad.careers360.com/articles/usmle-eligibility-criteria