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.
Social Security Number (SSN)
Please wait for CIEE’s email before applying for your Social Security. This application is mandatory if your internship is paid. It remains optional if you have chosen an unpaid internship or if you’re paid outside of the U.S.
The Social Security number has a lifetime validity (you don’t need to reapply if you already have one) and you’ll need it in order to get paid, open a bank account, and pay taxes. The American Social Security does not grant you health benefits in the U.S. It is only an administrative and fiscal identification number (your health insurance is covered by CIEE).
You will find further information regarding these two formalities on CIEE’s website.