Renault Megane mk1 (1996 – 2003)
The obd port on the mk1 is located in the main fuse box, behind a plastic panel on the right hand side inside the car.
Renault Megane mk2 (2002 – 2008)
On the mk2 the obd2 port is behind a plactic cover at the bottom of the center console, just below where you insert your keycard.
Renault Megane mk3 (2008 – 2015)
On the latest model of Megane, the obd2 port is located at the bottom of the center console below the radio and heater controls. Just pop off the plastic cover.