Glad it worked out for you @Johnie!
If you’re new to GMT, you really should go through the tutorial (https://docs.generic-mapping-tools.org/latest/tutorial.html) and the Cookbook (https://docs.generic-mapping-tools.org/latest/cookbook.html). The most important thing is however; try things out for yourself. Test and play with it. Make mistakes. You’ll learn alot from this.
I don’t know the technical details, but WSL has it’s own kind of filesystem, which is generally hidden from Windows’ that you’re used(?) to. You can run GMT everywhere you want, but assuming that you’ll use Windows programs to e.g. look at the figures, it’s best to work in a place easily accessable from both systems. I tend to use the desktop. To reach the ‘Windows filesystem’ you do:
cd /mnt/c
Try doing an ls -l; what you see should be somewhat familiar. Then go to your desktop:
cd /mnt/c/Users/<your username/Desktop
Make a file:
echo "Hello from WSL" > hello.txt
You should now see a file called hello.txt on your Windows desktop.
Make a folder and try to make a plot or two:
mkdir plot
cd plot
gmt psbasemap -R10/70/-3/8 -JX4i/3i -Bafg -B+glightred+t"My first plot" > my_first_plot.ps
If you’re new to the terminal and bash you might feel that the learning curve is steep, but once you get the hang of it becomes very powerful (as GMT itself).