If you are looking for a OnePlus 2 invite, try visiting the Airtel store (in selected cities). Airtel has partnered with OnePlus 2 and they will be handing out limited OnePlus 2 invite to customers on first come first basis.
All you need to do is check out the nearest Airtel store, you can check the URL here http://www.airtel.in/oneplus2/. What the consumer need to do is visit the store and get a hands-on experience of the OnePlus 2. They will need to upgraded to Airtel 4G and probably could win the OnePlus 2 invite along with the upgrade.
There are limited number of invites available and they will be given out on first come first serve basis.
You can know more about this smartphone and also check out the OnePlus 2 review here.