You must do two things as soon as you arrive in the U.S.
SEVIS REGISTRATION
This must be done within 20 days of your DS-2019 start date.
Log into your CIEE (Beacon) portal as soon as you arrive. A window will open up, asking you to register certain details.
You will receive a confirmation email within 2 to 4 days, inviting you to also register for your Social Security card.
You will find further information regarding these two formalities on CIEE’s website CIEE.