$ apm install linter-xo
Or, Settings → Install → Search for linter-xo.
Just write some code.
Settings can be found in the Linter package settings. XO config should be defined in package.json.
Note that it will only lint when XO is a dependency/devDependency in package.json.
This is to ensure it doesn't activate and conflict on projects using another linter, like ESLint.
We're considering a way to manually enable XO.
Automagically fix many of the linter issues by running XO: Fix in the Command Palette.
You can also have it fix the code when you save the file. (Only when XO is used in the project)
Enable it by going to; Settings → Packages → linter-xo → Settings, and then checking Fix On Save.