Anyone can apply for JEE main irrespective of category if he/she fullfill the JEE Main eligibility criteria

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

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

Central list of OBCs

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.

To apply for JEE Main you can refer below link

JEE Main 2018 Application Form

All the Best!!