Go through the entire JavaScript Codecademy course which you had started during your preparation for the assessment. https://www.codecademy.com/enrolled/courses/introduction-to-javascript

Any exercises that require you to create a pro-account can be skipped.

You may find the chapter “Objects” a bit hard to understand. Don’t worry about that. Try to understand it as well as you can, but if you don’t reach 100% understanding, don’t get stuck. There will be more opportunities to deeply understand the topic in future weeks.