If you go through the prospectus online it is stated there :
(i) Letters of Recommendation
The Postgraduate School, University of Ibadan, requires three letters of
recommendation from faculty members or others well acquainted with the
student’s academic work. Forms are provided for this purpose along with the
main application form. The Postgraduate School expects applicants to return
the recommendations by Referees sealed in separate envelopes, with their
signatures across respective seals. Such reports could either come along with
the main application forms or be mailed directly to the Secretary,
Postgraduate School, University of Ibadan before the deadline for the
submission of forms.
You can download a copy for yourself. If you know the deadline then it is clear from the above that you have to work with it.
Please when is the deadlineI need to know.