This is probably because Atom cannot find the executable (julia.exe). The same issue was reported here (HELP! "Julia could not be started " - #4 by Iulian.Cioarca), and there is a nice explanation from @Iulian.Cioarca
Go to the menu bar at the top of Atom. You should have a Juno tab with a lot of options. Scroll down to settings, and the Julia Client settings pane will open. There you will find a Julia executable path. Fill it with the julia.exe like:
C:\Julia-1.3.1\bin\julia.exe.
The path should have the version number from your installation, and if you installed it in the default location, it should be C:\Julia-1.8.2\bin\julia.exe.
Apart from that, I would also follow @jmair 's suggestion and switch to Visual Studio Code. Combined with the Julia extension, it gives a much better experience. I switched a few months ago myself.
Here is a great tutorial video https://www.youtube.com/watch?v=KesuPOlBB_o