To get an access on your ameli account, you first have to be registered with the Assurance Maladie (Health Insurance) and obtain a permanent social security number. 

This number (15 digits) starts with a 1 (for a man), or 2 (for a woman), then your year of birth (2 digits), month of birth, birth department (99 for people who were born out of France), birth county (3 digits), order number (3 digits) and a 2-digit control key.

If your social security number starts by 7 (for a man) or 8 (for a woman), it means that it is a temporary social security number.

You can create your ameli account only with your permanent social security number, using the first 13 digits.