Hi Yogesh, You can get the permit from DC office in Leh. You can get it online here: http://lahdclehpermit.in You can read more about the ILP for Ladakh here: https://goo.gl/WbMkeH Keep exploring!
Hello Sir, you dont need permit for Leh and the Ladakhi heartland region as OCI holder(considered as Indian National). However, you would need Permits for the Tso Moriri, Turtuk, Siachen and Nubra are easily arranged over a day from any of the many travel agents along Changspa lane in Leh.