When you are matriculated, you will automatically receive an RPTU account for students, which must be activated. You can activate it here.
To activate your RPTU account, you will need the initial password that was sent to you in the mail with your chip card PIN.
If you are a student of another university or university of applied sciences (Fachhochschule), you can get an account at the Service Point of the RHRZ (building 34/room 250).
Bring your valid student ID and an official photo ID (passport, driver's license, etc.).