[Used to be solved but a new problem exists yay] How do I import heightmaps into BeamNG?

Just as the title says, I want to import terrain heightmaps

 

Go to 7:12 in this video

 

Wow. Such a simple thing. Thanks for the help.
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Wait a minute, for some reason when I click import, my heightmap appears as a giant box

 

I couldn't do it too, but thanks for the video. Are you creating a map? Your Paypal donation link doesn't work.

 

He's not the one that made the video, he's working on a car atm.