Congrats on clearing your board exams. Yes, you definitely can appear for the DU JAT this year. It is conducted in the second or third week of june every year. Make sure to stay in touch with the du website as dates for registration and examinations are updated on it. 

DU JAT consists of 4 sections: verbal ability, general awareness, logical reasoning, quantitative ability. Your 12th percentage will only matter during the calculation of your JAT result but mainly the result will be focusing on the marks obtained in DU JAT. There will be negative marking so make sure you answer correctly, if you do not no the answer to any question prefer leaving it. Make sure to study well for the paper and solve the questions on time.

Thank you and feel free to contact for any other information.