You’re doing it right… download the navigation updater program, then use that to download the files to your 64 GB+ USB stick.
Currently, the most recent update (May 2023) is temporarily unavailable for all cars with the standard Gen5W system with navigation. So you’ll have to check back later when it is actually available again.
When you finally do get the update files on your USB, make sure you choose “quick update” when given the choice on the screen. But realize you are incredibly far behind and will be in for a multipart update. So there will be at least one time, probably even twice, where it looks like it’s done but it just keepa going. That’s normal.
Also, remember that your main home screen will change from your current three-tile setup to the modern dark, vague map home screen. A lot of people don’t realize this and are unhappy. But that’s how it’s been for the last six update versions… it’s here to stay.