Hi, to apply in 85% of seats under NEET UG, these are reserved for domicile students. For example if a resident (student) of Kerala who stays in Kerala wants to apply in a medical college of Kerala will be allotted a seat under 85% seats reserved for domicile candidates (any category).
So, to apply under 85% of seats you should have a valid domicile and also your schooling should be done from that particular state. You need to fill application form for your state level counselling seperately.

Hope this clears your doubt. Good Luck.