Okay i guess there is no Nagaland house in Pune. So to visit Nagaland you anyway have to come to northeast and have to go through the gateway to northeast; Guwahati. So, what you can do is visit Nagaland House in Guwahati, located in Sixmile, Sachal. You'll need any Govt. ID. 2 passport size photograph, And 100 rs charge for the ILP. Ph. No. 0361-2332158. When you are in Guwahati you can locate Nagaland house in Google Map. A very easy destination to find out. You have to be on the GS (Guwahati-Shillong) road. I hope that helps.
Nagaland ILP cannot be applied online so if you want ILP you will have to visit the Nagaland House in your city or state or in Guwahati. Its not much of an issue for tourists to enter Nagaland as most of the time they check your ids and let you enter...but thats all luck. Its best to be on the safe side and get the ILP.