Hi
You can appear in JEE Main, if you wish to get admission to National Institute of Technology (NITs), Indian Institute of Information Technology (IIITs), & Centrally Funded Technology Institutes (CFTIs). However, if you wish to get admission to Indian Institute of Technology (IITs), you will have to qualify JEE Advanced, which is the next level entrance exam of JEE. Both are national level entrance exams. Since you belong to UP, I would suggest you to appear in UPSEE, which is a state level entrance exam. I would advice you to score minimum 75% marks in your class XII exams to avoid any sort of problems at the time of admission.
There are engineering entrance exams at university level too. You can write back to me to know about them.
JEE Main 2018
UPSEE 2018
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