This is a simple, and (Trust me) a short tutorial on how to make a terrain heightmap for the terrain editor using paint . net. So letZ get into it!
Quick Disclaimer: I automatically assume you know how to use paint . net, if not I suggest you watch some youtube videos on how to use it / find buttons
Part 1:
First of (if you haven’t already) lets get paint . net at this link: Download (Paint . net only works on windows. Sorry mac and linux users 
)
Ok so let me clarify this there is also a paid version of paint . net, and also it is not only used for terrain! It can be used for many other useful things too!
So once it’s downloaded you want to open it.
Once it’s open close your current project like this (Don’t worry it won’t close paint . net. Just your project 
):
Now your screen should look like this:
Create a new project.
Now your screen should look like this:
Now for some math (Our favorite subject i’m sure lol). 1 Pixel = 4 studs on roblox. So if you want a 2000 stud map then just set the width, and height to: How many studs of land you want / 4
So in my case I want (Lets say a 2000 stud map) so what I can do is divide 2000 by 4 then that will be 500! So lets make a 500 pixel wide, and 500 pixel tall map.
This is what it should look like:
Once you click ok you should get a new project.
Now click ‘Turbulence…’
You should end up with something along the lines of this:
Here are going to be my settings for the "Heightmap generator":
Notice how I set “Period” to 450. Its close enough to 500. The reason I set it to 500 is so we almost match up with our Height and Width settings we set earlier (After we converted studs to pixels using math… Our FAVORITE subject in school lol).
Once you click ok then your screen should look a little something like this(Results will / can vary):
Now save your heightmap so we can import it to our place.
Part 2:
So now all we have left to do is to import this into roblox studio!
So once roblox studio is opened go to a published place (I suggest you do this in a test place and not your actual roblox game) make sure the game explorer is open
Then click import at the bottom of the game explorer window, then upload the “Terrain Heightmap” image we generated using paint . net!
Now you must wait for the image to be moderated / approved by roblox moderators.
Once it has been approved open the terrain editor, click on Import
Now click on 'Asset Id':
If you have uploaded some images already, then “Scroll around” until you find the "Heightmap" we made in paint . net. Then click on it.
Then we want to set our X, and Y size to 2000 studs (Because I mentioned earlier in the topic we were going to make a 2000 x 2000 stud world) keep in mind that we are setting this to 2000 studs because of the math equation: Size of our "Heightmap" in Pixels x 4:
Don’t worry about the "Colormap" settings below the settings we were working with. As you can see… The "Use Colormap" slider is toggled off. Once you are done with everything you can click on Import
Now your terrain will appear! 
:
Note that it’s material will be asphalt (Because thats the default material for "newly" imported terrain xD)
Hopefully this tutorial was helpful! And don’t forget to paint your terrain so it looks better.
Anyway thanks for stopping by, hopefully this tutorial was helpful, and don’t forget to drop a screenshot of the terrain you managed to create with this tutorial.