If you are unable to find the Preview HTML option in the Atom editor after right-clicking on your code, please follow the steps below:
Go to the Packages then Preview HTML and then click on Enable Preview.
If you are unable to locate the Preview HTML in the Packages then go to the File and then settings.
Go to the Install and search the package atom-html-preview and install the one published by harmsk.
4. If you right-click, you should now have the Preview HTML option.