Your Writers Work profile is designed to put the focus on what really matters: your writing! Thus, the writing samples you use in your portfolio should reflect the skills and interests that you want potential employers to know about. Whatever the genre, style, or subject matter, each sample should reflect your talent as a writer.
If you have previously published work that is available online, you can link to it in your portfolio. If the work is not available online, you can copy it into a new document in the Document editor, save it, and link to it. You're also welcome to use anything else you have written, whether it was something you wrote for school, something you published in a blog, or something you wrote on your own.
You can add as many writing samples to your portfolio as you want, but it's recommended that you have at least two to three pieces in your portfolio.