The University of Nigeria hereby invites candidates who made UNN their first-choice institution in the 2020 Unified Tertiary Matriculation Examination (UTME) and scored 180 and above for screening exercise.
Eligible candidates are required to pay a processing fee of N2,000.00 (Two thousand Naira only) through Remita Platform at any Commercial bank.
The online registration commences on Wednesday, August 5, 2020 and ends on Friday, August 28, 2020.
Here are the steps and process for the online registration

Process Flow for Post-UTME Registration
Log on to the University Website: unn.edu.ng
Click on UNN portal (Top right corner of the Website)
Click Prospective Students
Select Online Application Form for 2020/2021 Admission Screening Exercise
Enter JAMB Registration Number
Generate Invoice
Proceed to bank for Payment or pay using your ATM Card
Return to Portal
Re-enter JAMB Registration Number
Complete Date of Birth and all other blank fields
Enter O/Level Subjects and Grades (also provide your Centre and Examination Number. Note: Awaiting Results candidates should list their SSCE subjects)
Re-enter your grades correctly
Upload Certificates (Ensure that their sizes are not above 100KB)
Birth Certificate
Local Government Identification
Testimonial
First School Leaving Certificate
JAMB Result Slip
O/Level 1
O/Level 2 (For double sitting candidates) and click the NEXT button


Review Summary Page and check that all details entered are correct
Check the CONFIRMATION BOX below
Click SUBMIT
Print Acknowledgement Slip.

DIRECT ENTRY CANDIDATES FOR 2020/2021 WHO MADE UNN THEIR FIRST CHOICE INSTITUTION SHOULD ALSO REGISTER FOR THE SCREENING.
For more information please click on the link below
Source:http://saintbillion..com/2020/08/university-of-nigeria-nsukka-begins-her.html?m=1

There's a thread that has been since 2017.
You may find useful information on it.

https://www.nairaland.com/3811417/university-nigeria-nsukka-unn-aspirants