For JRF you need to clear UGC NET exam which is conducted twice in a year. For JRF candidate should be below 30 years and thus the competition is high. Check the previous year questions and patterns and then start prepare accordingly. Do give mocks from the official website also read newspaper daily for GK.

Check the link

https://www.google.com/url?sa=t&source=web&rct=j&url=https://competition.careers360.com/articles/ugc-net-eligibility-criteria/amp&ved=2ahUKEwicmIaR5qjqAhWXaCsKHf8nBUAQFjAAegQIBxAB&usg=AOvVaw3TWklAovQ5Qa_auMAbKFyQ&ampcf=1

Good luck