With a 35 MM Camera setting you can set your camera to one of the 4 corners as your red X shows and it will utilize most of your terrain, if that is what you are asking about, but I always use a 50 MM camera as it doesn't distort the outer edges like the 35 MM. Also, it matters little if you use the function editor to import the map or use the picture importer on the near to the bottom left in the terrain window, that is when figuring in your mats they will create different details of their own.
 
You may also want to render smaller sections of your terrain to use as individual terrains and you can distribute them anywhere you want.
In World Machine2 there is an 'Ortho World" view and you pick the details where and when you want them to render and export as individual maps, then mix and match later. I prefer that method.

I would rather be Politically Incorrect,
Then have Politically Correct-Incorrectness!!!