Hello Rizwan!
Central Universities Common Entrance Test (CUCET), is a national level examination that is conducted every year to provide admission in various UI(Undergraduate/5 yrs-Integrated), PG (Postgraduate) and RP(Research Programs) offered by 18 Central Universities of India.
So, to get admission in any one among these 18 Central Universities, you'll have to participate in CUCET-2020.
The last date to apply for CUCET has been extended till 23rd May, 2020.
You can apply online, check the list of universities accepting CUCET scores, list of courses offered, eligibility criteria for the individual institutes, get the syllabus and model question papers w.r.t. your course etc. by visiting the official website : https://www.cucetexam.in/
This year, CUCET will be conducted by the Central University of Rajasthan (CURAJ).

For the other Central Universities like Jawaharlal Nehru University (JNU), University of Delhi (DU) etc., universities conduct their individual entrance exams.
The last date for filling up JNUEE-2020 application form has also been extended upto 31st May, 2020. You can apply for it by visiting: http://ntajnu.nic.in

For DU admissions, no notification has been released yet. There is only the news about postponement of its admission process until further notice due to COVID-19 outbreak and lockdown in the country.

If you are interested in any other University or have any more queries in this regard, kindly provide its name or ask your doubts in the comment section.

Hope this answer will help you.