Thank you for catching up that discrepancy in the installation guide, I already corrected it.
.rar is just one of the many formats (like .zip) used for compressing files. Unfortunately, I don’t have a macbook to provide a step-by-step guide, but I recommend looking up tools that are available and compatible with your system for extracting .rar files (you can try “winzip” or “unarchiver”, for example). If you’re not sure how to use them (or want to try something else), you can try searching for “how to extract .rar files macbook [program you want to use]”, or any other similar search.
I hope this works for you.