I'm guessing here, but ...
The part "Download the current flight data file to your Palm add-on folder." is done by clicking the
Schedules: Palm - Macintosh.
This downloads a file called "onepalm.sit" - I guess you need to store it or its contents in your "Palm Add-on Folder" or similar.
A .sit file is a "StuffIt Archive" file.
Not having a Palm - Macontosh, I'm not sure where you need to go after that.