There are 4 national categories General, OBC-NCL, SC & ST so you need to check the category.

You can check below list of state wise category who comes under OBC NCL centralized category list:

Central list of OBCs

SC

http://socialjustice.nic.in/writereaddata/UploadFile/Scan-0026.jpg

ST

https://tribal.nic.in/ST/LatestListofScheduledtribes.pdf

If you apply through OBC-NCL, SC or ST category you have to show your valid certificate which is centrally valid at the time of counselling or admission. If you fail to show your certificate they can cancel your admission in reserved category.

If you are not in the list then you can appear as general caregory student.

To apply for JEE Main you can refer below link

JEE Main 2018 Application Form

All the Best!!