How do I connect adafruit 2.8 TFT Touch Shield (1651) on mega2560 ?
First of all, please post a link to the actual shield that you have.
Any UNO shield can fit on a MEGA2560. The Adafruit shield uses a strange mix of pins. If your software works on a UNO it should be possible to work on the Mega. However you may need to edit the software.
Adafruit provide tutorials on using with a Mega, https://learn.adafruit.com/adafruit-2-8-tft-touch-shield-v2/connectingread that page. You need to add solder jumpers as described.