In case you're not meeting the requirements yet OR you simply need brief refreshers: There are two sections at the end of the course that get you started (Section 18: "Bonus: JavaScript Refresher" & Section 19: "Bonus: React.js Refresher").

Those sections are optional and you can ignore / skip them if you already got the requirements.

But in case you're interested, you can jump forward to those sections and go through them first before you continue with the course.