I am on Step 6, and I am able to download the Google Drive file, but it opens in Numbers in my Mac. I am not able to avoid this process, and even when I export the Numbers file to a CSV on my desktop, it still does not transfer to Salesforce properly. It says unmapped, but there is nothing I have done wrong on any previous steps in any of the previous labs.

Well if Numbers opened it, then the file is downloaded onto your computer somewhere, probably in the Downloads folder. Are you not able to find it there?
If not, try emailing me and I'll attach the file to my reply.