Sony just mentions it briefly, but you need to reformat the SD card before dropping the BODYDATA.DAT firmware file in the SD card.
If you do not know how to format a SD card, check this guide here: https://support.garmin.com/en-US/?faq=QqSbC0YZTz57kLm7uRQxZ7
You should format the card as FAT32. exfat is also doable, but it is not compatible with older android devices (like the herelink), so a user would not be able to plug the sd card into a herelink to view images if it was exfat
Below are screenshots from the website. Instructions may change when new versions come out. This is just 2.00
Here is a video of me uploading the firmware. Note: I already did the SD card stuff before this video