Replicate the folder structure on the SD and set your unit to use external storage.
Copy GPX files to NewFiles or existing .fit files to the Courses folder and it will use them.
Always check that all your files appear in the Courses list - the 800 has an issue where it will just ignore some files dropped into NewFiles. I've had this happen many times and have to keep copying the missing file(s) until they all appear. Numbering them makes this easier.
You should store everything to external SD card.
Replicate the folder structure on the SD and set your unit to use external storage.
Copy GPX files to NewFiles or existing .fit files to the Courses folder and it will use them.
Always check that all your files appear in the Courses list - the 800 has an issue where it will just ignore some files dropped into NewFiles. I've had this happen many times and have to keep copying the missing file(s) until they all appear. Numbering them makes this easier.