Mission planner get Terrain Data and flight using it

I am trying to get terrain data from gcs and sent it to the flight controller. I have generated terrain data at my end and store it into .dat file. now I want to store that file into flight controller’s SD card, but I didnt know any way to do it.
I received TERRAIN_REQUEST message from FC and in response I have to sent TERRAIN_DATA message. I didnt understand that what parameter need to be sent as data in this TERRAIN_DATA message.
I am using these mavlink messages as reference as stated in mission planner documentation mentioned below.

I just want to ask that is this a correct way of doing it or am I doing it wrong? also how mission planner get the terrain data and conduct flight using it.