Macbook Air Updates

I recently bought the app education bundle, and when I went to download and redeem my codes, it said I needed to be at IOS 10.15, after updating my 2017 MacBook twice, I realized that I am only at 10.13. I am very frustrated because there seems to be no way to quickly get to the newest version, so now I have to wait to download the apps that I just paid $200 for. Is there any way to get to 10.15 quickly that I do not know about?