Firstly call the mobile operator customer care from mobile( 121, 198 etc). Verify your SIM card ID, address and other details
Carry your Adhaar card along with a passport photograph to nearby company store.
They may deduct some charges from your mobile balance. So you'd need to have some mobile balance. For example Vodafone deducts some Rs. 25 as processing charges.
They will give you a new SIM which will be activated within 2-4 hours.