New user a couple of questions

First things first.

What are you using to try to import this map?

I use L3DT. Use to have videos up on tiled terrain but I have removed them.

You need to make it a r16 heightfield and size it to the UE standard. Here are some wiki pages to get you started.

https://wiki.unrealengine.com/Landscape_-_Sizes_and_Height_Guide

https://wiki.unrealengine.com/World_Machine_to_UE4_using_World_Composition