In class 12 I have only 66% in best four subject
I hope the 4 subjects that you're talking about are physics, chemistry, maths/biology and English. Then yes this percentage are enough as the criteria to get eligible to apply for universities through an entrance exam. As per JEE criteria, you won't be allowed since you need 75 and above in all the 4 main subjects. But you can apply for NEEt, cet, bits and other exams and then on that merit score you can surely get a college as you pass the 10+2 eligibility criteria.
Or else with 66% if you want do pursue BSC, or other courses like this, then you can get into them too. Of course you won't get the best college but surely a good one.
Best wishes. Thank you.