Here is the image from advertisement.
To activate this offer on your broadband just send a SMS DELIGHT to 53636 from your mobile number registered with Airtel or Otherwise you can fill-up your broadband details in this web page to activate this offer.
As per the customer care, activation should take at-most 96 Hrs and it should double up both day and night time surfing speeds!
Wait for few more days to know my results.
Update: This offer is not available for variable speed plan customers like me. In variable speed plan your surfing speed is changes during morning & the night time.