When you open the link, you should see a picture of hands holding a pencil. (This is a copy of the pages found in the WWE instructor text.) Scroll down and you will see the first diagnostic evaluation. Start with that one. If your student passes it, move on to the next one and so on.
A student will not necessarily be in the same level of WWE as in First Language Lessons (the elementary grammar curriculum, FLL), or at "grade" level, so it is important to use this diagnostic tool.
In 2014, Susan Wise Bauer wrote updated guidelines for using our writing program based on the first years of customer feedback. Writing With Ease, Writing With Skill Recommendations. These recommendations are "baked in to" The Well-Trained Mind, 4th Edition, published in 2016.