https://play.google.com/store/apps/details?id=com.gigato.market
Open the app
.

Register your account.

Submit your details.

You will get Recharge in few seconds.
Others Details:
1. App compatible with android 4.1 and above,

2. All indian operators supported for the free data offer.
3. The offer cannot be clubbed with any other offers.
4. The free data can be used to browse any app,website like normal data upto the limit for plan.
5. Offer available only for a limited time period.
6. The offer will provide you 2G/3G data depending on your circle,operator.