A maximum of 5colleges can be added where your score will be sent out of participation institute  

So after logging in and filling and uploading all documents go to School preference section and add schools. For more than 5, each school added shall add cost of rs200.

All details below

https://bschool.careers360.com/articles/nmat

http://www.nmat.org.in/test-takers/register-and-schedule/