The eligibility test to hire for Group B and C positions, the UPSSSC PET, is conducted yearly. If you want to apply for various positions and examinations under the ambit of UPSSSC, you would need to register and apply for the same through PET. The UPSSSC PET exam will be for 2 hours and in pen-and-paper mode.
Link: https://www.cheggindia.com/govt-exams-blogs/upsssc-pet-answer-key-2/