Try including the css file to see if you are satisfied with the result. It should work, but if you want it to look different you should include your own styles. You can use the provided css file as a starting point.
From the parsley.js docs:
"Parsley adds many classes and elements in the DOM when it validates. You are strongly encouraged to customize them in your own stylesheets, but here is the "standard" Parsley css file that is used here on the documentation and examples, if you want to use it to bootstrap your projects with Parsley."