You must go to the relevant department (UFR) to ask for a liaison document then go to the Central Registration Office to withdraw a notification and an enrolment file.
You will gain access to: - classes in the amphitheatres, - the inter-university library, - tutorials, subject to the lecturer's agreement according to the number of students.
Note
You do not have student status (notably for the medical insurance plan specific to students).
The syllabuses followed will not be validated (no examination, no degree).